Porsche 917 Super Profile 0854294953, 9780854294954

Citation preview

:John A\llen

a

ISBN 0 85429 495 3

A FOULIS Motoring Book First published 1986

© Haynes Publishing Group All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage or retrieval system, without written permission from the publisher,

|

Published by: Haynes Publishing Group, Sparkford, Near Yeovil, Somerset BA22 7JJ

Haynes Publications Inc.

| 861 Lawrence Drive, Newbury

Titles in the Super Profile series Ariel Square Four (F388)

BMW R69 & R69S (F387) Brough Superior SS100 (F365) BSA A7 & A10 (F446) BSA Bantam (F333) BSA Gold Star (F483) BSA M20 & M21 (F485) Honda CB750 sohe (F351) Matchless G3L & G80 (F455) MV Agusta America (F334) Norton Commando (F335) Norton International (F365) Norton Manx (F452) Sunbeam S7 & S8 (F363) Triumph Thunderbird (F353) Triumph Trident (F352) Triumph Bonneville (F453) Velocette KSS (F444) Vincent Twins (F460)

Park, California 91320 USA

British Library Cataloguing in Publication Data

Allen, John S, _ Porsche 917 super profile. —

(Super profile) |

|

1. Porsche 917 automobile — History | [ite ll. Series

6292222 11215 P75 ISBN 0-85429-495-3 Library of Congress catalog

card number 86-80181

AC/Ford/Shelby Cobra (F387) Austin A30/A35 (F469) Austin-Healey Frogeye’ Sprite (F343) Austin-Healey 100/4 (F487)

Cover photograph: by Neill Bruce, courtesy of Midland Motor Museum _ Photographs: Andrew Morland, Neill Bruce, Geoff Goddard, Kremer Racing, Porsche Road tests: Courtesy of Autocar and Sport Auto Printed in England, by: J.H. Haynes & Co. Ltd

Lotus Elan (F330) Lotus Seven (F385) MGB (F305) MG Midget & Austin-Healey Sprite (except ‘Frogeye’) (F344) Mini Cooper (F445) Morris Minor Series MM (F412) Morris Minor & 1000 (ohv) (F337) Porsche 91171 Carrera (F317)

Rolls-Royce Corniche (F417) Triumph Stag (F342) Deltics (F430) Great Western Kings (F426) Gresley Pacifics (F429) Intercity 125 (F428) V2 ‘Green Arrow’ Class (F427) Further titles in this series will be published at regular intervals. For information on new titles please contact your bookseller or write to the publisher.

| Chevrolet Corvette (F432) Datsun 240Z, 260Z and 280Z (F488)

Ferrari 250 GTO (F308) Ferrari Daytona (F535)

Fiat X1/9 (F341)

Ford 100E Anglia, Prefect & Popular (F470) Ford Consul/Zephyr/Zodiac Mk 1 (F497) Ford Cortina 1600E (F310) Ford GT40 (F332) Ginetta G15 (F496) Jaguar E-Type (F370)

Jaguar D-Type & XKSS (F371)

Editor: Mansur Darlington Page layout: Chris Hull _

Jaguar Mk 2 Saloons (F307)

Jaguar SS90 & SS100 (F372) Lancia Stratos (F340)

i

days’ comments.

It was brought

into existence thanks to a loophole

Followers of sports car racing will know that, as in most sports, there are good years, and there are bad. Recently, the bad have been outnumbering the good, with the arrival of Group C in 1982 having

improved matters only slightly, Porsche’s superb 956 obtaining such a stranglehold on the sport that no longer are there any significant newcomers willing to challenge it. It was not always thus, for in the period from 1964 to 1971 sports car racing was extremely healthy, with a wide variety of makes vying for the honours. That period saw first Ferrari, then Ford, and finally Porsche, emerge as top dogs, but whilst the three were fighting amongst themselves there were plenty of only slightly lesser breeds snapping at their heels. Nostalgia often lets us recall only the good, but in truth there must have been something rather special about those days. Attendances at race meetings prove it; there was once talk of up to 300,000 spectators at Le Mans, whilst nowadays the paying guests number little more than 20 per cent of that figure. Porsche’s ultimate weapon, developed towards the end of that eight-year period, was the 917, a car which still brings forth ‘Those were the 4

in the Manufacturers’ Championship regulations, and It was so good that a change in the rules was necessary so that it could be outlawed to give others a chance. Thus excluded from contesting the premier championship, Porsche turned to the lucrative and hitherto liberally regulated Can-Am series, where the developing 917/30 so overwhelmed the other competitors that once again it had to be outlawed. Its final fling was in the Interserie, where it ruled supreme until, yet again, rule changes prevented its further involvement. There being no more championships left for it to win, the 917 was retired to museums and to historic racing. If you were not fortunate enough to experience at first hand that heyday of sports car racing, you may find it difficult to understand the awe in which the 917 was held at the time. If, however, you had seen that cliffhanger of a race at Le Mans in 1969, where overpowered and undertyred 917s were fishtailing violently as they left the pits, been privileged to watch disbelievingly as Rodriguez threw his 917 around the rain-soaked track at Brands Hatch in 1970, or witnessed the battle between Donohue’s Ferrari and the langheck Porsches of Siffert, Rodriguez and Elford at Le Mans in 1971, you would know why the 917 is remembered with something akin to reverence.

In writing this Super Profile | had to call upon the assistance of several people whom | am now pleased to thank. David Piper was extremely helpful, providing his car for photography and uncomplainingly putting up with my questioning. Klaus Parr and Jurgen Barth, both of Porsche, provided invaluable photographs and information, as did Kremer Racing’s Achim Stroth, whilst Alan Hamilton gave me details of the Australian connection. My thanks go also to Autocar, for permission to use the Mark Donohue interview and report from their 11 May 1974 issue, and to both Sport-Auto and José Rosinski, who allowed me to include a translation of the latter's report on the Gesipa 917K, originally published in the magazine's July 1970 issue. John

S Allen

or

st

Porsche’s Sports Cars Way back in 1951, Frenchmen Veuillet and Mouche shared the wheel of a little Porsche 356 through 24 gruelling hours at Le Mans; by the time the race had ended they had brought the works-entered 1086cc car up to a very respectable 20th position, and had become the first in a long line of drivers who would ensure that every subsequent 24 heures du Mans would see participation by cars built by the Stuttgart manufacturer. For year after year, Porsches put up some splendid performances, often winning the small-engine classes and occasionally posing problems for some of the bigger-engined cars. _The year 1964 saw what could be called the first truly modern Porsche, the mid-engined 904, which on a tight circuit could hold its own with virtually anything that the opposition could pit against it. There followed the even better 6-cylinder 906, the 910 which was very successful in 1967, and the super-streamlined 907. All these cars were solid, reliable, extremely nimble, ... and | underpowered.

Class victories may be fine to

some, but it is not the class victories which grab the headlines, the headlines which provide the . publicity needed to sell sports cars. No amount of good placings at Le Mans could provide the sort of publicity which surrounded the outright winners, the Jaguars, Ferraris, Mercedes and Fords. To have any hope of catching the big cars, Porsche would have to build their own big ones, and for a manufacturer whose whole philosophy was based on small, agile, cars, the prospect of competing in the major league was daunting. It was late in 1967 that the opportunity came, out of the blue. There had been mounting concern about the high speeds which were being attained by the fastest sports cars of the day, and in a bid to limit speeds, and so avoid the disastrous accident which some said was bound to occur, the rules for sports car racing were changed dramatically, at less than six months’ notice. For the 1968 season, the maximum engine size allowed for prototype sports cars was to be reduced to 3 litres, thus eliminating the Fords, Ferraris, Chaparrals and Lolas which had proved to be the fastest cars of 1967. It did not take Porsche very long to take stock of the situation, and to realise that the existing 2.2-litre 907 could easily be modified to a full 3-litre, the resulting car first appearing as the type 908 in April 1968. Porsche were not the only ones to see the 3-litre limit as just what they needed; the French concerns of Matra and Alpine Renault were not slow to produce their own 3-litre cars, and later they were joined by yet more manufacturers. Porsche expected (with good reason, as it turned out) that the other 3-litre cars would not pose much of a threat, but there was just one small cloud on the horizon. For the four years from 1968 to 1971, ‘production’ sports cars, homologated in the then Group 4 as having been built in a te

ull

minimum quantity of 50, would be allowed to use engines of no less than 5 litres capacity. The cars that were eligible for this concession were the old Ferrari 250LM, the relatively new and unproven Lola T-70, and the as yet unsuccessful small-block variant of the GT40. For some reason best known to themselves, the sport's rule-makers, the CSI, also lowered the required production quantity to 25. Even so, the odds were that the bigger-engined cars would be too heavy and too cumbersome to compete with the 908, which thus began the 1968 season as firm favourite for the Manufacturers’ Championship. The surprise of the 1968 season was that the GT40 proved both as fast and as reliable as the 908, and ended up with both the Championship and Le Mans to its credit. Porsche’s chance of the one victory that really counted — Le Mans — took a further knock with the spreading of rumours that Ferrari were about to start a production run of 25 5-litre sports cars for use in 1969. There was no alternative for Porsche; if they were not to watch their best-ever chance of an outright win at Le Mans slip from their grasp, they had to act quickly, and take the plunge that they had so long avoided — they HAD to build a big car.

The 917 Programme In view of the time scale which faced Porsche — they wanted their new car to be competitive by June, 1969 — the company wisely elected to base the newcomer on existing designs. The aluminium tube chassis owed much to that of the 908, the aerodynamics were almost pure 908, adapted only to cover a slightly wider and longer chassis, and even the engine had details in common with that of the 908. The problem which outsiders 13)

said would never be overcome was that of keeping the engine cool. Porsche’s adherence to air-cooled engines had always been seen as an insurmountable hurdle in the manufacture of engines of much over 3 litres, and the proposed 4.5 litres of the 917 would be breaking entirely new ground. Work commenced on the project in July, 1968, and throughout the rest of the year no word of it leaked out. The more observant commentators noted that the provisional entry list for Le Mans 1969 contained two entries for Group 4 Porsches, ostensibly 910s, but why the factory should choose to drag out a two-year old design was a puzzle. Could Porsche be intending to substitute something more interesting? On 25 March 1969, at the Geneva Salon, the mystery was solved, with the unveiling of Porsche’s wonder weapon.

The 917 had arrived.

Design At the heart of the 917 was its engine, an enormous flat-12 which pumped out some 580bhp. The crankcase was cast in magnesium, the power take-off being central, effectively splitting the engine into two sixes placed end to end; this avoided the torsional problems which could otherwise have been expected to afflict the crankshaft. Cylinders were cast aluminium, the bores being chrome-plated. Only two valves were provided per cylinder, in the twin-plug aluminium heads. Naturally, the power unit featured four overhead camshafts, these being driven by gears from the central crankshaft gear. The 8main bearing engine was equipped with dry-sump lubrication and kept supplied by fuel via a Bosch fuel-injection system. Cooling proved to be less of a problem than had been anticipated, and

6

was achieved by means of a plastic fan placed horizontally above the cylinders. Behind the engine was fitted the Porsche 5-speed gearbox, with full synchromesh, and the limited-slip differential, the transmission being linked to the engine via a triple-plate dry clutch. Completing the drive train were the titanium drive shafts, each featuring twin universal joints with the addition of rubber doughnuts to cushion the transmission. Wheels were of 15-inch diameter, those at the front being a mere 9 inches wide, whilst those at the rear measured a more respectable 15 inches.

Porsche's predilection for weight saving was obvious in the chassis; despite its strength, the aluminium tube frame weighed in at an amazing 47kg (104 Ib)! This superb piece of engineering ensured that the complete car scaled only a mite over the 800kg minimum weight limit set for the class. As late as 1968, Porsche had been constructing their spaceframe chassis from steel, but successful experiments with the 908 in that year had shown that aluminium could be used, with negligible loss of strength and stiffness, so the latter material was used for all production 917s except for five experimental cars, which adopted magnesium for their chassis. Visually, the 917 resembled a stretched 908, but in fact there were some important changes to the overall proportions. The extreme length of the engine and gearbox resulted in the cockpit having to be much further forward

than in the 908, in order to retain the 908’s 90 inch wheelbase. Unlike the 908, which had been available in both long- and short-tail versions, the 917 used an ingenious design based on the style of the long-tail 908, but with the rearmost 9 inches being detachable. This permitted the private owner to ensure that his 917 was in the correct configuration for the track being visited: long-tail for faster circuits, short-tail for use on tighter tracks. Each version of the tail used movable aerodynamic devices, these taking the form of two small spoilers or flaps, overhanging the extreme rear of the tail. The flaps were connected, by an intricate series of levers, to the rear suspension, and were so arranged that they acted independently. As the bodywork on one side rose, ie when cornering, so the flap on that side rose too, producing extra downforce to counteract the body lift. The system had been used earlier on the 908, and appeared to work well. At the other end of the car, downforce was provided by two rather vulnerable canard fins on the lower part of the front fenders. One aspect of the bodywork which allowed quick recognition of the 917 was the lower sills, which were cut away at the rear, so that the exhausts from the front six cylinders could exit ahead of the rear wheels; the engine's other six cylinders exhausted at the back of the car in the normal way.

Into Action Only sixteen days after the car had stolen the show at Geneva, two examples arrived at Le Mans to take part in the annual test sessions, intended to give manufacturers some opportunity to try out their hardware well in advance of the race itself. The 917s were quite impressive,

although they weren't trying to be; the object of the exercise was to collect data, not to break records. Already the pundits were beginning to mutter about the advisability of letting the 917 loose amongst private entrants, some suggesting that there simply were not enough drivers of the calibre necessary to cope with the car, of which no fewer than 25 would have to be built before any would be allowed to race. With that number built, the company would be forced to sell many of them off, to recoup the enormous initial outlay, and a price had indeed been set — a very reasonable £14000.

Homologation If there is one subject which is likely to cause problems and anguish in motor racing circles, it is homologation. This is the procedure whereby manufacturers attempt to persuade the sporting authorities to accept that the maker’s new car complies with all the relevant regulations and, most importantly of all, has been built in the required numbers for the car to be admitted into the appropriate production car category. There have been some unfortunate differences in the application of the rules, one of the most obvious occurring when the Ferrari 250LM was accepted into Group 4, which required a minimum production of 50 vehicles, when only 32 had in fact been constructed. Having been duped on more than one occasion, the CSI let it be known that Porsche would have to provide. very strong evidence of there being 25 917s before homologation would be granted. Porsche did just that; in an unprecedented move, they built up all 25 required cars and lined them up in a neat row outside the factory at Zuffenhausen. Faced

with incontrovertible proof that _

the cars actually existed, the CSI immediately granted homologation. The 917 was ready to go.

A Season of Disappointments Along with the usual fleet of 908s, Porsche took a pair of the new 917s to Spa Francorchamps in May. The Belgian circuit, much disliked by the Grand Prix fraternity for its alleged inherent dangers, featured some long straights and sweeping curves, and appeared to be ideally suited

to the immensely powerful 917.

iS

2H

—

During practice, the drivers made it quite clear that they believed the 917 was unsuitable for Spa (and any other track, for that matter), all of them preferring to drive the nimble 908. Eventually, Gerhard Mitter and Udo Schutz drew the short straw, and aligned one of the 917s in eighth place on the grid, behind the 908s (of course), a Mirage, two Lolas and a 3-litre Ferrari. The dreaded 5-litre Ferrari had been no more than a rumour — was the 917 effort to have been in vain? As the cars moved off, Mitter missed a gear on the 917; the engine revs soared, a piston met a valve and the new Car's race was over. Although the flat-12 was fitted with an electronic rev-limiter, the threat of over-revving was always to hang over the 917. When a shift was missed, the limiter could not act quickly enough to prevent engine speed from exceeding 8500rpm, usually with terminal

effect for the valves. The 917’s début had been brief indeed, and it was not until the annual running of the ADAC 1000km race in early June that there was a real opportunity of assessing the 917’s performance.

The old Nurburgring has always had the status of a classic circuit. Its 14-mile length, twisting up and down through the Eifel mountains, has proved to be one of the toughest tests for driver and car alike, and some say that no sports car can be truly great unless it has been victorious in the © 1000km there. If that were so, then the 917 would have to be removed from the list of the greats, as it never shone on the ‘Ring's’ tortuous track. In 1969, the call for volunteers to man the sole 917 was met by all the Porsche ‘pilotes’ promptly taking one step backwards. The problem was solved by recruiting the assistance of BMW works drivers Quester and Hahne. Everything was fine until the BMW Board heard of the arrangement and, horrified, immediately banned their drivers from the wheel of the still unproven car. Eventually, David Piper and Frank Gardner were enticed to Germany to take over, with the instruction that they should finish the race at all costs. They did remarkably well, and for six hours they took turns at fighting the 917, keeping it out of the scenery and bringing it to the chequered flag in a creditable 8th place, being beaten by the 908s, the class-winning GT40 and a 2-litre Alfa Romeo T-33. By this time it had become obvious to everyone that the handling of the 917 left a great deal to be desired, but, unfortunately, those at Porsche did not know the reason for the problem. Chassis flexing seemed a likely cause but tests showed that the chassis was not the culprit. With only two weeks to go before Le Mans, there was little that could be done, so all efforts were put into preparing four long-tail

cars as well as possible for the 24 Hours. It was hoped the handling difficulties would not be so noticeable at the Sarthe. There is something about Le Mans which sets it apart from other events. No matter how good, or how bad, the entry, the interest in Le Mans. is always far greater than in any other sports car race, and its prestige is probably matched only by Indianapolis. The 917 was intended from the outset to become Porsche's first Le Mans winner, so it is not surprising that the company should take the race extremely seriously, with the four-car spearhead of the 917s being supported by four 908s, of which three were long-tail coupés, the fourth being an open-topped car fitted with a lengthened, finned, tail. Right from scrutineering there were upsets. The twin movable spoilers on the tails of the 917s were declared illegal, following a recent change in legislation which sought to ban the flimsy wings which had a habit of falling off Grand Prix cars. Despite Porsche's spoilers being quite strong enough for them to be a hazard to nobody, the 917 and the 908 were both caught by the new rules. Porsche argued that because the 917 had been homologated with the movable flaps the car should be allowed to use them in the race; surprisingly, their case was accepted by the scrutineers, but only after Rolf Stommelen had demonstrated a 917 with the flaps fixed in one position; in this condition the car was virtually undriveable. For the 908, however, there was to be no such concession, the cars all having the flaps rendered immobile. The other significant problem concerned drivers who, once more, expressed a preference for the 908; this time, however, the preference was not as marked, because the 917 was without doubt the fastest car on the track, Stommelen recording a superb time of 3m 22.9s during practice, to take pole position for the race.

8

One of the new 917s at Le Mans had been handed over to Englishman John Woolfe, in whose name it had been entered, and who was to be the first customer to take delivery of a 917. Woolfe had hoped to field a McLaren, but the non-homologation of McLaren's M6GT had ruled that out. His regular co-driver, Digby Martland, was most unhappy with the 917’s handling, and considered the car was dangerous; he refused to drive it in the race, his place being taken by works driver Herbert Linge.

ae

At the start — still the traditional run across the track and leap into the car — Stommelen was first away in his 917, the car fishtailing wildly as the tyres sought some grip. He was followed by Elford in the second works 917, then a bevy of 908s, Ferrari 312Ps and then the rest of the field. There was no third works 917, that car sitting out the race rather forlornly in the paddock, as Porsche did not have enough drivers to crew it. Right away there was drama, at the tricky White House curves. Some say that Woolfe’s 917 lost a door which then struck the rear fins, whilst others reported that he was going too fast, and put two wheels onto the grass. Whatever the reason, Woolfe lost control, and the car left the track, struck the banking and promptly broke in two, exploding as it did so. The driver died on the way to hospital. The debris from the crash was spread over the track, and was the cause of one of the Ferraris

retiring, as Amon’s 312P burst into flames on striking the Porsche's burning fuel tank. Despite the tragedy, the race, of course, continued, and for the most part it was dominated by Porsche. The Stommelen/Ahrens 917 was considerably delayed by clutch troubles which eventually caused its retirement, but the other 917, of Elford and Attwood, led comfortably after Siffert’s fast 908 had stopped with a broken gearbox. Through the night the 917 droned on, drawing out an ever-increasing lead over the remaining 908s and the Gulf GT40 which was proving to be a thorn in the side of Porsche. With 21 hours of racing behind it, the 917, which had been reaching 236mph on the Mulsanne Straight, finally relinquished the lead when the gearbox casing split allowing oil to seep on to the clutch. The 917 challenge was gone, and Porsche's hopes for a first-time victory vanished along with it, the remaining 908 of Hans Herrmann and Gerard Larrousse being unable to hold off Jackie Ickx’s GT40, which beat the Porsche by a mere 2 seconds at the end of 24 hours of racing.

Taming the Beast It is rare for a racing car to become an immediate winner, and the 917 had proved itself no exception. Perhaps what is most surprising is that it took relatively little effort to turn the ill-handling 917 of 1969 into the refined reliable car which swept aside all opposition in 1970. Much of the credit can go to Porsche's arch-rivals of 1969, JW Automotive Engineering Ltd, who were signed up during 1969 to become Porsche's front line team for 1970. The breakthrough came at a testing session at Zeltweg in October, 1969, attended by representatives of both Porsche

and JWAE. A 917 coupé was being put through its paces by Kurt Ahrens, Brian Redman and Leo Kinnunen, none of whom felt at one with the big car. JW’s John Horsman noticed that whilst the front of the car was splattered with the squashed remains of dead insects, the car's tail was relatively clean, indicating that comparatively little air was hitting the tail. Mechanic Ermanno Cuoghi suggested that the coupé be fitted with the tail from the Can-Am spyder (of which more later) which was also present at the session. As it was impracticable to adapt the spyder’s tail to fit the coupé, the mechanics set about the coupé with hacksaws, aluminium sheet, tinsnips and rivets. The new tail which resulted was hardly pretty, its raised fenders doing nothing to reduce drag, but it was certainly

effective. At a stroke, the 917’s handling had been transformed. The new tail provided all the downforce that had previously been lacking, and took away the viciously unpredictable handling that had made the 917 so very disliked. It was never to become thought of as a nimble car, its great power, heavy engine and forward driving position preventing that, but by 1970 it had lost the vices which had made it feared.

1970 was something of an anti-climax after the dramas of 1969, but the season did see some exciting contests between the 917

and Ferrari's answer, the 512S. The Italian cars scored only one victory, at Sebring, and the Gulf/JW 917s took most of the remainder. It fell to Porsche Salzburg (the Austrian wing of the Porsche empire), who were running. another quasi-works team, to take care of Le Mans, which they won with their standard 4.5-litre 917K, the drivers being Hans Herrmann and Dickie Attwood. Works-supported 917s missed only two Championship

events, the Targa Florio and the Nurburgring, both being considered as favouring small cars; 3-litre Porsche 908/03s mopped up those two rounds.

Although the competition presented by the Ferrari 512S appeared to be overcome quite easily, Porsche were actually putting a great deal of effort into ensuring that the 917 remained truly competitive throughout the 1970 season. The aerodynamics having been sorted out satisfactorily, attention was at last given to improving the car's mechanical specification. The first major change was the adoption of an enlarged engine, as the original size had not taken full advantage of the 5-litre limit dictated by the then regulations. The 4.5-litre size employed the same bore and stroke as the 3-litre 908, and had been used simply as a matter of expediency. During early 1970 tests were undertaken with a 4.9-litre, in which the stroke was increased from 66 mm to 70.4mm. The bigger engine was first used by Porsche Salzburg,who raced a pair of 917s in most of the 1970 Championship races. They were in direct competition with the official works team, the Gulf-sponsored JW Automotive, but it seems that the management at Porsche actively fostered rivalry between the two teams. Porsche had not forgotten their love of long-tail cars, and at the Le Mans test weekend in April they appeared with a brand new car featuring much sleeker bodywork than previously seen on any 917. The ‘Venetian blind’ perspex engine cover was replaced by a plain, small transparency, and the tail was fitted with a pair of large fins. The nose was more pointed than before, the headlights being repositioned under lengthened fairings. The new shape met with the approval of Porsche Salzburg, who were willing to try anything to enable them to beat JW Automotive, but the latter team viewed the new shape with some

distrust. Although they could acknowledge that the streamliner had less drag than the conventional 917K, and was therefore faster down the Mulsanne Straight, they believed that the new shape had the disadvantage of reduced downforce, and was accordingly more difficult to handle through Le Mans’ fast, sweeping curves such as Maison Blanche. The new langheck was used only at Le Mans, where Vic Elford qualified his Salzburg car in pole position for the June race, but was to retire when a valve failed; the long-tail which John Wyer had refused to run was passed on to Hans- Dieter Dechent's Martini Racing Team, and eventually finished a creditable 2nd. JW Automotive had replaced their cars’ ATE brakes with British-built Girlings, which were at least 10 per cent more efficient than the German ones. Surprisingly, patent problems prevented Porsche themselves from fitting the Girling units, but several private teams, including Martini in 1971, modified their cars accordingly. Other modifications for 1970 included a Borg & Beck clutch which had sintered metal linings, and a revised gearbox which could be used as either a 4- or a 5-speed. The gearbox casing was strengthened following the failure of one of them at Le Mans the previous year; that breakage had probably cost Porsche the race. 1970 had seen Porsche victorious both at Le Mans and in the

International Championship for Makes, as the sports car championship was then known. Ferrari had been utterly trounced, the 512S usually being slower than the 917, and almost always being much less reliable. The big Ferraris had suffered more than their share of bad luck, during 1970, and Porsche could not afford to be too complacent. Indeed, all complacency was swept away at the Osterreichring

on 11 October, when the Ferrari works team was represented by a single, modified, 512S, driven by Jackie Ickx and the up-and-coming Ignazio Giunti; although the Ferrari ultimately retired with electrical problems, it proved to be faster than the 917s, and made Porsche realise that more effort was going to be needed if they were to control 1971 as they had 1970. To ensure that the message was well and truly driven home, the same 512S (later rechristened 512M) won the Kyalami 9-hour race in South Africa. Everything pointed towards 1971 becoming a memorable year.

Final Revisions to the

Coupé Having already taken the 917’'s engine size out to 4.9-litres, Stuttgart went the whole hog and introduced a full 5-litre version during 1971. The extra 500cc over the original engine allowed output to increase to around 630bhp, a very useful 50bhp bonus. Much attention was once more paid to aerodynamics, although this time the target was low drag rather than increased downforce. The standard K-type tail provided downforce in plenty, but its drag-coefficient was woefully high, so it became the object of extensive wind-tunnel testing. The new design which resulted was essentially similar to the 1970 style, but had a lower fender line at the rear, and two high vertical fins. It was made to be interchangeable with the Daytona 70 tail, thus giving teams the choice of two tails, each with different drag/downforce characteristics. The search for the ultimate long-tail car continued, and was to prove so successful that even John Wyer accepted the new car for JW Automotive to race at Le Mans. It is probably fair to say that 10

with the 917 the study of vehicle aerodynamics took an immense leap forward which has not been equalled before or since. The old adage of ‘if it looks right it is right’ was thrown away, and Porsche began the development of cars in which efficiency in cutting through the air took priority over prettiness of line. The result was visible in such extreme vehicles as the 917/20, a grotesque parody of the 917 in which the bodywork was widened to such a degree that the wheels were incapable of effecting the smooth flow of air over the car. On both the /20 and the 1971 /anghecks the nose was squared off to allow as little air as possible to go under the car, Porsche being the first company to realise that air squashed under a car causes both drag and lift. Research was not confined to aerodynamics; the chassis frame came in for some attention, the most promising development being the use of magnesium tubes in place of the earlier aluminium. Magnesium is lighter, but more difficult to work, but the weight saved (around 5kg on a 917K chassis!) was considered to be worth the effort, for although the car was already down at the minimum permitted weight, every kilo saved allowed more important equipment to be fitted in its place. As luck would have it, at Le Mans in 1971 all the favoured long-tail cars retired, and the 917’s second victory at the Sarthe was achieved by the only magnesium-framed 917K ever to race.

The 1971 season was not quite as good for the 917 as 1970 had been, because the opposition from some of the new 3-litre cars proved to be extremely strong. The Ferrari 512M was abandoned by the works, despite the car's obvious potential, for Ferrari chose instead to concentrate on developing the 3-litre 312P for 1972. At least the 917 came away with a victory at Le Mans, achieved the fastest lap ever recorded on a road circuit (Siffert’s 162.09mph at Spa), won the fastest race ever held on public roads (Spa again, at an average speed of 154.77mph), recorded the shortest ever lap time at Le Mans, covered the greatest distance so far during the 24-hour race, and won no fewer than seven of the eleven rounds of the Manufacturers Championship!

Group 7 Racing Porsche’s entry into the world of Group 7 racing was a low-key affair, undertaken with a single open-topped 917 during the Summer and Autumn of 1969. The Canadian-American Challenge Cup series, known universally as Can-Am, was open to unlimited displacement sports cars, and was renowned for its lack of restrictive rules, competing cars having to be two-seaters with covered wheels, but in most other respects being unlimited. A pair of special 917s was built in 1969, the two cars being dubbed 917PA, the PA standing for Porsche-Audi, who were to sponsor the American adventure. Mechanically, the two spyders were virtually identical to the coupé 917, and it was principally in their open coachwork that they departed from their predecessors. Because they used a basically standard chassis, they were very nearly as heavy as the coupés, and were not expected to take Can-Am by storm.

One of the two spyders was retained at Zuffenhausen to act as a test and development vehicle, while the other was shipped to North America for Siffert to drive in seven of the eleven Can-Am rounds, starting at Mid-Ohio in

August. The PA was too heavy to allow its 580bhp 4.5-litre engine to make it competitive against the all-conquering 7-litre McLarens, but the car proved to be very reliable, and in the five rounds which it finished it never ended up lower than 5th overall. In the Championship, Siffert was an excellent 4th, the achievement being the more remarkable because he had missed the earlier rounds in the series. The 917PA lay unused throughout 1970, as Porsche had more important tasks to consider. That year did, however, see the inception of a European answer to Can-Am — the Interserie, which was mainly contested on German circuits but also took in visits to Finland and the UK. Several 917K coupés took part in the first year, and it became obvious that the series was ideally suited to the 917, particularly if converted to spyder form. When it became known that 1971 was to be the last year that cars of over 3 litres would be allowed to compete in the International Championship of Makes, Porsche switched the emphasis of the 917 programme away from the coupé and towards the spyder, with the intention of developing it into a fully-competitive Can-Am car. Initially, three coupés were converted into spyders for use in the Interserie, but one of the three was virtually a new car, even to the extent of having a new chassis in it. Over in the USA, the original 917PA which had been used in 1969 was entrusted to Vasek Polak, who entered it in the Can-Am series with Milt Minter as driver. Whilst the Interserie cars remained in essentially the same form as the original PA, the latter car itself was extensively modified

by Polak, ever seeking improved aerodynamics; the front end was squared off, radiator ducting was greatly enlarged, and the tail was fitted with pressure relief vents plus a pair of streamlined vertical fins. It ended up more efficient,

but considerably uglier, than when it had started. Minter came 6th in the Can-Am championship that year, but his achievement in the, by then, 4.9-litre PA was overshadowed by Siffert in a brand new car, the first purpose-built Group 7 Porsche. The arrival of the 917/10 heralded a new era in Group 7 racing, as the American V-8s were about to be eclipsed by Stuttgart’s flat-12. The latest 917 made full use of the freedom given by Can-Am regulations, and had many improvements over earlier 917s. Fuel capacity was taken up to 300 litres, so as to avoid the necessity of refuelling during a race of 200 miles or so, and the use of exotic alloys (such as the titanium of the rear hubs) ensured that the car was considerably lighter than the 917K coupé. Naturally, spyder bodywork was used, to keep weight down and reduce frontal area, the car initially resembling a rather squarer version of the PA. Porsche spent a great deal of time investigating the 917/10’s aerodynamics, and succeeded eventually in endowing it with a downforce, at 200mph, equivalent to the weight of the car. This was obtained in conjunction with considerable drag, the /10’s Cd ranging from 0.551 to 0.656 depending on its configuration. Because the car was used mainly on tight circuits, a good drag co-efficient was of less importance than downforce, so the trade-off was one that Porsche were quite willing to make. As with the PA before it, the 917/10 missed the first few rounds of its début Can-Am season, and did not appear until “the 1971 Watkins Glen event. Siffert was its driver throughout

the remainder of the series, and although he scored well the car was still underpowered in comparison with the front running McLarens. None the less, the 68 points he amassed before his tragic accident at Brands Hatch were sufficient to give him 4th place in the 1971 Can-Am series. There were two avenues for Porsche to explore to try to find the power needed to win in Can-Am, and so the company investigated both of them. One way was to develop an even larger engine, the 16-cylinder motor which resulted being of 7.2-litres. The alternative approach was to enter virgin territory by adapting a turbocharger installation to fit the existing engine, and it was this latter route which led to the most powerful racing car that has ever been seen. The first step was to fit twin Eberspacher (later renamed KKK) turbochargers to a 917/10 to be used by Mark Donohue. To Porsche can go most of the credit for developing turbocharging to the position where it can now be used routinely on road cars, but before it got to that position Porsche had a great deal of work to do. The principal obstacle to be overcome was throttle lag, as the turbo had to be spinning at maximum speed — about 90,000rpm — before it could provide maximum boost. It also suffered from lag on the over-run continuing to feed the cylinders momentarily after the throttle had been closed. The use of 1.3 bar boost required the compression ratio to be lowered, the resulting 6.5:1 not helping the car’s torque characteristics, and thus compounding the throttle lag problem. The problem was overcome by fitting blow-off valves which opened as the accelerator was closed, permitting the turbines to continue spinning without having to contend with back pressure from closed-off valves. The first version of the engine to race was of 5-litres capacity, and it proved to be more 17

than adequate to see off the McLarens and to bring the Can-Am Championship to Porsche for the first time, with George Follmer taking the honours, Donohue having been injured in an accident early in the series. In Europe, 4.5-litre versions of the turbo engine were supplied to Interserie competitors, enabling Leo Kinnunen and Willi Kauhsen to come first and second respectively in the 1972 series.

The Fastest of Them All As if the 917/10 were not enough, the ultimate development of the 917 appeared in 1973, and was made available only to Roger Penske’s team for Mark Donohue alone to drive. The new 917/30 featured an engine enlarged to 5.4-litres, producing a phenomenal 1,100bhp in race trim. The gearbox was of the type which had been developed for the turbo 917/10, and was a 4-speed sufficiently strong to withstand the turbo engine’s massive torque. The clutch, too, had to be strengthened, a Borg & Beck 4-plate unit replacing the earlier 3-plate. The wheelbase was lengthened, following tests with the first prototype, which used an ingenious chassis design which was of adjustable wheelbase. As the car was longer, it could accept larger fuel tanks, these being of 400 litres (88 gallons) capacity, which were certainly needed in view of the new engine’s thirst (about 3mpg). The 917/30 featured a longer tail than on the /10, the new design being so efficient that it was later to be used, virtually unchanged, on the 1976 type 936. Donohue débuted the car at the first Can-Am race of 1973, at Mosport, and immediately put it on pole position, although in the race he was delayed after tangling with a slower car (they were a// slower) and having to pit for repairs to the bodywork. Minor TZ

fuel problems slowed Donohue’s 917/30 in the second race in the series, but he won the remaining five events without being seriously challenged. It was too good to be true, and in the face of increasing complaints from other Can-Am competitors, the Sports Car Club of America used the so-called ‘Energy Crisis’ of 1974 to bring in new fuel consumption requirements which effectively ruled the 917/30 out of contention. Can-Am has still not recovered. Before being despatched to museums, there was just one further task awaiting the 917/30s. The Penske team took a car to Talladega, where Donohue drove it round the banked NASCAR track; with the provision of additional intercoolers and other cooling aids, the 5-litre car lapped the circuit at an average speed of 221mph, a record which remained unbroken for six years.

Return of the 917 For several years the 917 became a historic racer, with owner-drivers using their venerable machines to delight the crowds at supporting races all over the world, although the car had been legislated out of big-time racing. Spectator interest in the sports-racers of the late sixties and early seventies remained high, and over the winter of 1979/80 the Kremer brothers embarked on a courageous project to build themselves a 917 from scratch. Over a long period they had been collecting parts wherever they could, and it got to the stage where a new 917 became a feasible proposition. They were in the throes of rebodying an Interserie spyder back to coupé configuration for its English owner, who agreed to allow the Kremers to retain the car for as long as it was needed to act as a master to be copied. Full drawings and technical information were

made available by Porsche, and construction began of a new chassis to form the basis of a 917 which would be indistinguishable from an original. Work was progressing when Kremer’s sponsors, Malardeau, heard of the car, and persuaded the builders to adapt the 917 so that it could be used as a fully-fledged racing car at Le Mans in 1981. Yet another rule-change had meant that, for one year only, Le Mans and the sports car championship would be open to cars which conformed with what was dubbed ‘Group 5/75’, ie open-topped sports cars complying with 1975 regulations, but without engine capacity limits. The 917 was tailor-made for this category, and the Kremers’ new car duly appeared at the Sarthe in June 1981. Naturally it was the centre of attention — there was much talk of ‘the Good Old Days!’ — but in the event it did not really shine, being undergeared during practice, and having mostly indifferent drivers. After retiring from Le Mans with engine trouble, the 917K81 raced only once more, at the Flying Tigers 1000km at Brands Hatch. This time, Bob Wollek, the only experienced driver of the trio who had handled the car at Le Mans, shared the 917 with three-times Le Mans winner Henri Pescarolo. The pair put in a spirited performance, and in the early part of the race harried the new Ford C-100 for the lead. When the Ford retired, the crowd was to witness a 12-year-old design in the lead at Britain's premier sports car race! It was not to last, and the car eventually left the road when a steering component failed. The Kremer 917 went into retirement as a display car at the company’s Cologne premises, but its performance at that championship race at Brands Hatch had left no one in any doubt that the 917 was truly one of the world’s greatest sports cars.

1 June 1969, Nurburgring By finishing in 8th position, the short-tail 917 004 becomes the first 917 to complete a race. 14-15 June 1969, Le Mans

The /anghecks make their first race start, with 917 007 and 917 008 both representing the works team, 917 006 as spare and 917 005 as the first car to be raced by a private entrant.

10 August 1969, Osterreichring First victory, with short-tail 917 009 narrowly beating a Lola T-70. 17 August 1969, Mid-Ohio Début of the 917PA, alias the Can-Am Spyder, Jo Siffert finishing fourth in 917 028. October 1969. Zeltweg Where limited production racing cars are concerned, it is often inappropriate to chronicle detail changes in strictly numerical order. Modifications were made sometimes on brand new cars leaving the works, and sometimes on elderly machines which had already seen their fair share of action. The purpose of this chapter is to present a chronology by which the development of the 917 can be traced, highlighting all the significant changes undergone by, and events in the career of,

Testing with 917 008 leads to the development of the revised tail design which is to transform the 917’s handling. 8 November 1969, Kyalami 917 010 appears with an interim tail design which foreshadows that of the 917K. 11 January 1970, Buenos Aires 917 010 becomes the first car to use the standard tail unit, later dubbed the ‘Daytona 70’ tail.

Porsche's first big, car.

July 1968, Stuttgart Design studies of the type 917 begin. 13 March 1969, Geneva The first prototype, 917 001, appears at the annual Salon. 29 March 1969, Le Mans Still unhomologated, two long-tail cars, 917 002 and 917 003, make the type’s first track appearance at the test weekend.

20 April 1969, Stuttgart 25 917s are lined up at Zuffenhausen for inspection by the CSI's representative; homologation is granted, to take effect from 1 May, 1969. 11 May 1969, Spa The short-tail coupé, 917 O05, makes the 917’s first race appearance.

1-2 February 1970, Daytona The 24-hour race sees the début of the definitive 917K, featuring modified front intake ducting and the Daytona 70 tail. Three examples, 917 011, 917 014 and 917 015, start the race. 25 April 1970, Monza Following tests with 917 022, the ’ 4.9-litre engine is used for the first time, being fitted in 917 023.

17 May 1970, Spa JW Automotive use a variation of the standard tail, with the central valley upswept at the rear, on 917 014 and 917 017; the design is not used again. 11-12 April 1970, Le Mans An improved /angheck, 917 041, featuring much sleeker lines than the 1969 version, participates in the test weekend. 13-14 June, 1970, Le Mans Further revisions are made to the two /anghecks, 917 042 and 917 043, which start the race, the most obvious change being removal of the plexiglass fairing over the engine. JW Automotive’s three cars, 917 016, 917 017 and 917 026 have winglets fitted between the two tail-spoilers. 4 April 1971, Brands Hatch Experimental air-intake scoops are fitted over the injection trumpets of 917 020; engines of a full 5-litre capacity are used in Gulf cars 917 029 and 917 035. 18 April 1971, Le Mans The test weekend sees the first appearance of the ‘Truffeljager’, alias 917/20 001, which subsequently takes part in the 3-hour race. Also present is 917 052, making the first public appearance of a magnesium chassised 917, and featuring a reshaped short tail, fitted with twin fins. 917 043 reappears, its longtail body having been improved since the previous year, and now incorporating faired-in rear wheels, a horizontal full width rear wing, and squared-off lower front body contours, in the hand of Jack Oliver the car records a fastest lap of 3m13.6s, the shortest ever lap time at Le Mans, with an average speed of 155.6mph, which speed is not beaten until 1985.

25 April 1971, Monza Twin vertical fins are used on revised tail units fitted to 917 017, 917 020 and 917 034; the design subsequently becomes standard for use on faster tracks. 2 May 1971, Imola The start of the Interserie sees 73

Cam-Am Spyders in private hands for the first time, 917 007, 917 021 and 917 031 being present. 12-13 June 1971, Le Mans First and only race appearance of the 1971 /angheck as seen at the test weekend; all three cars, 917 042, 917 043 and 917 045 retire, allowing victory to go to 917 053, the only magnesium-framed 917K. to take part in a race. 27 June 1971, St Jovite Can-Am car 917 028 reappears, its bodywork much modified to increase downforce. 25 July 1971, Watkins Glen 917/10 002 makes the first race appearance of the series 10 Can-Am car. 3 April 1972, Nurburgring The Interserie race includes 917/10 004, the first example to use a 5.4-litre engine. Both it and 917/10 002 have new tail units which incorporate twin vertical fins joined by a horizontal wing. 11 June 1972, Mosport Mark Donohue introduces the first turbocharged Porsche, 917/10 011, which has a 5.0-litre engine and a magnesium frame. The bodywork is revised to include a shovel-nose profile.

14

9 July 1972, Osterreichring The turbocharged engine is made available to private teams, and is used in 917/10 002 and 917/10 004, the latter also having the newer nose design. 20 August 1972, Mid-Ohio Rear wheels of 19 inch width are made available for all 917 /10s. 10 June 1973, Mosport Final development of the 917, the series 30 Can-Am car, makes its début in the hands of the Roger Penske team; having qualified on pole position, Donohue’s 917/30 002 is delayed by an accident, eventually finishing 7th. 22 July 1973, Watkins Glen 917/30 002 scores the type’s first victory in the Can-Am race; the remaining five Can-Am races of 1973 will all fall to the 917/30.

28 October 1973, Riverside The last race appearance of a works-supported 917 results in a

win for Mark Donohue in 917/30 003. 13-14 June 1981, Le Mans A 917 returns to the Sarthe! After an absence of nine years, the car’s comeback is made by the Kremer Brothers’ 917K81.

Type Designations

Porsenesg1 7,9) 70H 291 7K 917PA, 917/10, 917/20.917/30

Chassis Numbers 917 coupé with detachable long-tail 917K short-tail coupé 917PA Can-Am/Interserie spyder 917LH long-tail coupé 917/10 Can-Am/Interserie spyder 917/20 Le Mans coupé 917/30 Can-Am spyder

Total

917 001 to 025 917 026 029 to 032, 034 to 036, 044, 051 to 053 SiPsO27 0287083 917 040 to 043, 045 917/10 001 to 008, 010, 011, 015 to 018 917/20 001 917/30 001 to 004

25 |2 3 5 14 1 4

To the total of 64 chassis listed above can be added the single 917K81 built by Kremer Racing in 1981. Not all the chassis listed were supplied as complete cars, and in some cases the chassis concerned were still incomplete in 1985. Of the initial production batch, at least 20 were rebuilt to 917K specification. Some cars have been rebuilt around un-numbered chassis, while in other cases numbered chassis have been used as replacements in damaged cars. Several 917Ks were converted into Interserie spyders (and back again) and certain 917s have been known to exchange identities, for example for customs and carnet purposes. Consequently, the production total should be considered as approximate only, and references to cars by specific chassis number are subject to the foregoing points. Manufacturer

Engine Crankcase Cylinders Heads Bore Stroke Capacity BHP/rpm Torque (Ibf ft)/rom Compression ratio Camshafts Injection Lubrication Transmission Clutch

Gearbox Ratios

(Porsche)

Dr.Ing.h.c.F. Porsche AG, Stuttgart-Zuffenhausen, Germany 1969 917 1970 917K 1971 917/10 1973 917/30

Magnesium, 8 Magnesium 8 Magnesium 8 Magnesium 8 main bearings main bearings main bearings main bearings 12, Cromal 12, Cromal 12, Nikasil 12, Nikasil Aluminium, 24-valve, with twin plugs per cylinder 86mm 86mm 86.8mm 90mm 66mm 70.4mm 70.4mm 70.4mm 4494cc 4907cc 4998cc 5374cc 580/8400 600/8400 630/8300 1100/7800 376/6600 415/6400 425/6400 820/6400 MORORI Ona Oost 61531 4 OHC 4 OHC 4 OHC 4 OHC Bosch Bosch Bosch Bosch, with 18.5 psi turbocharger Dry sump, oil pressure 35 psi Fichtel & Sachs Borg & Beck Borg & Beck Borg & Beck 3-plate 3-plate 3-plate 4-plate 4 or 5-speed 4 or 5-speed 4 or 5-speed 4-speed When the 917 was first made available to private entrants, sets of 33 different gears were provided, these allowing for correct gearing for virtually every occasion, although during 1970 and 1971 further gears were used from time to time. The original set provided for ratios as follows: First: 2AG2e2 308-2:2155 2.072) 2,000 11 934517624

Seconds

(2,000, 1.934, 1.824, 1.723, 1.612, 1.527, 1.429, 1.381, 1.319 i[bs)

1973 917/30 1971 917/10 1970 917K 1.429, 1.381, 1.319, 1.239, 1.167, 1.125, 1.080, 1.044 1.000, 0.959, 0.926, 0.889, 0.859, 0.834, 0.808 As for fourth, plus 0.786, 0.759, 0.741, 0.719, 0.700, 0.678, 0.656, 0.634 Using the standard final drive ratio of 4.625:1, and with tyres as used in 1969, the 1.000:1 4th/5th gear gave 28.9kph (17.96mph) at 1000rpm. Optional final drive ratios were 4.428, 4.444, 5.285 and 5.375:1.

1969 917 Third: Fourth: Fifth:

Track Front Rear

1488mm/58.6in 1457mm/57.2in

1582mm/62.3in 1533mm/60.4in

1620mm/63.8in 1584mm/62.4in

1670mm/65.7in 1565mm/61.6in

4780mm/ 188.2in 4290mm/ 168.9in

4120mm/

162.2in

3740mm/ 147.2in

4560mm/ 179.5in

Width

2033mm/80.0in

1980mm/78.0in

2080mm/81.9in

2100mm/82.7in

Height

920mm/36.2in

940mm/37.0in

1145mm/45.0in to top of fins

1080mm/42.5in to top of fins

Aluminium

Aluminium

Aluminium

Aluminium

Length

Chassis

(Tubular spaceframe)

Suspension Front

(upper adjustable) with lower Independent, transverse wishbones trailing radius rod; titanium coil springs: Bilstein co-axial shockabsorbers; adjustable anti-roll bar. Independent, transverse wishbones (lower inverted), both adjustable; longitudinal control arms; titanium coil springs; Bilstein co-axial shock absorbers; adjustable anti-roll bar.

Rear

Bodywork

Fibreglass

Fibreglass

Epoxy

Epoxy

Wheelbase

2300mm/90.6in

2300mm/90.6in

2300mm/90.6in

2500mm/98.4in

Steering

Rack and pinion, right hand drive

Brakes Ventilated discs 12in

ATE

ATE/Girling

Porsche

Porsche

9 x 15in 12 x 15in

101/2 x 15in 15 x 15in

12 x 15in te xX 15in

12 x 15in 19 x 15in

Tyres Make Front Rear

Dunlop 4.75/11.30-15 6.00/13.50-15

Firestone 5.50-15 10.10-15

Goodyear 9.40-15 15.70-15

Goodyear 9.0/24.0-15 14.5/26.0-15

Fuel capacity Litres Gallons (Imp/US)

140 31/37

120 26/32

300 66/79

400 88/106

Dry Weight

800/1763

800/1763

734/1618

849/1872

0.590

0.575

Wheels (magnesium) Front Rear

(Kg/Lbs)

Drag Co-efficient (Cd)

0.330 (long-tail) 0.447 0.400 (short-tail)

Racing car specifications rarely remain unchanged for long, and a car may undergo extensive modifications which can have multiple effect. For example, the adoption of wider wheels plus rear-mounted fins can alter tyre sizes, track, height, length, weight and drag; for this reason, the above specifications should be regarded as typical but not definitive. 16

Gl C1 & C2. During 1970 and 1971 917Ks were raced by three teams which enjoyed full works support and, between

them, they managed to account for every 917

victory in the Manufacturers’ Championship in those years, Porsche Salzburg used 917 023 in a white livery on its first outing, at the 1970 BOAC

1000km,

but by

the time Le Mans came around it had been repainted as shown in photo C7.

/t gave Porsche the company’s

most cherished victory, with Hans Herrmann and Gerard

Larrousse winning the 24-hour race, and it was subsequently retired to Porsche's superb museum

in

Stuttgart. In terms of the number of victories, JW Automotive Engineering Ltd were the most successful quasi-works

team, achieving eleven wins in

championship races. For much of 1971 they used 917 0716, seen in photo C2 at Brands Hatch in that year, as

their test car. /t was fitted with the extra roof-window used at Daytona, so as to provide the drivers with a better view, because on the circuit's banking the visual

effect for the driver is similar to when driving on an ever-steepening hill.

C3 (below).

The third works backed team was Martini

Racing, who took over Salzburg’s cars at the end of 1970. Looking rather worn after its victory at Sebring in 1971, 917 020 is shown here during practice for the 7000km race at Brands Hatch,

where van Lennep and

Larrousse took it to 9th position.

Ce rh A Oreos

ee BR wet eset'

~

e

nee

i

4st

&

4 &

SONG

|

aie

C5 (opposite).

JW received two langhecks, prepared at

the works, to use at Le Mans in 1971, this being the Rodriguez/ Oliver car, 917 043. During practice, drivers of all the langhecks complained about /ack of ventilation,

which was provided via three NASA

set into the nose panel.

Various improvements

ducts were

tried,and the solution finally adopted was achieved by means

of trunking drawing air from circular holes set in

the extreme front of the car, as shawn in photo three langhecks being so equipped.

78, all

Despite being

designed specifically for Le Mans, no langheck ever won there; 917 043 was destined to retire when an oil-line ruptured, starving the engine of lubricant.

SEAL fats

C6 (above).

Porsche pioneered the now routine practice

of bringing a supply of spare body panels to a race.

At

Le Mans in 1977 these two tails were awaiting use if called upon, but fortunately neither was needed.

They

present an interesting comparison between long and short versions, and it is easy to see how the 19717 finned short-tail derived from the 1970 langheck. Both

these pieces of fibreglass had seen use on the track, the short one had come from 917 052, which had been

dismantled following the Le Mans

Test Weekend in

1971, whilst the longer unit was from 917 042, the Elford/Ahrens Salzburg entry at Le Mans in 1970.

C7 (right). David Piper’s 917K shows well the earlier type of Kurz tail, with deep valley between the rear

fenders (compare with the much shallower version in photo C6). Rear spoilers were adjustable for height. Note that the chassis tubes are clearly visible, and that the wheels were open at the back; from

1972 onwards

most regulations demanded that the wheels should have deep splashguards fitted.

C8 (opposite top). Porsche’s magnificent flat-12 is a

very large engine, and a tight fit in the rear of 917 010.

With the fibreglass guard removed, the intake trumpets become

visible. Each is protected by 2a bung which

will

not be removed until the engine is about to be run, as it

is all too easy for the massive trumpets to swallow debris.

The cooling fan is also in fibreglass, and turns at

0.895 of engine speed; at Le Mans in 1970 one of the Gulf 917Ks broke its fan drive, and it was said that the fan then imitated a helicopter, and flew over the Dunlop

Bridge! Bracing for the roll-over bar was added to the car fairly early in its history, but is not a factory fitment.

C9 (opposite bottom). Inner fenders show where the

fibreglass has been extended to cover tyres which are wider than those originally fitted. The gearbox rests beneath the chassis tube pyramid,

whereon

the Group 5

racers carried a ‘Spacesaver’ spare wheel and tyre.

C10. A dry sump engine requires a separate oil tank, the

917’s being situated alongside the engine, on the left of the car. Note the Bosch fuel-injection pump and the fuel collector tank.

C11. The offside front suspension shows the adjustable upper wishbone.

What appears to be a crude caliper

actually directs cooling air onto the ventilated disc.

SEL

AAE

AMEMAABLEPLENLS

| TT CRT PR,

er

tl

ee

‘

.

C12. At only 37 inches high the 917K isa

removable.

remarkably low vehicle. 917 010 has a one-piece front body panel, the usual lift-out section being unnecessary. due to. the entire front being

The lip ahead of the oil-radiator vent

the outlet, drawing

opening helps create a low pressure area above

warm air out.

C13.

In an attempt to enable the 917 to breathe more

easily, these air scoops one race appearance,

the 1971 BOAC

reappeared,

were tested, and they made just on Martini Racing's 917 020 in

1000km.

Two weeks /ater they

this time on Gulf’s 917 016 at the Le Mans

Test weekend,

but the scoops

were found to increase

Syl

Note that the side window

ee

ena

ae7a, aay

drag by about 5 per cent, more than enough to offset any horsepower gained, so they were then abandoned

MS —

fF

/ ee /

had been modified to allow

it to be kept open.

C14.

Interserie spyders were very similar to the original

PA, but they had only one season in which to prove their worth, as they were overwhelmed by the 917/10

from the start of 1972.

Ernst Kraus ran this spyder in the

1972 Interserie, the car being seen here at Silverstone in May of that year, Kraus finishing 4th on aggregate in the two-heat event. Kraus’s best finish of the series was

a 3rd place at the Coppa Shell di Imola. in the Championship,

He came fifth

taking a total of 34,800 Swiss

Francs in prize money.

26 rena rs8 warn

deena ermmaeTietaniit! te ete

meses Leh

harman em le aeaahopaatea Me nc

COA at mA

sswhash pees

tt DE

AIC

NOONAN

EARN

: EON

Ne

ae

nom

-

—

a

C15 (left). During 1969 917s were raced by the factory's own team, under the banner of Porsche

System Engineering. 917 007 was entrusted to Rolf Stommelen and Kurt Ahrens at Le Mans,

where it

qualified on pole but spent much of the race in the pits, having its clutch attended to, before eventually retiring after only nine hours.

The car was /ater rebuilt as a

standard 917K, and became the Gesipa Rivets team car.

This night-time photograph shows the dark red seats, the alignment markings for each of the filler caps, and

the almost central steering wheel. Right hand drive was used on all 917s because most circuits are used ina

clockwise direction, and it is best to have the driver's

weight to the inside on corners, although with the 917 the cockpit was so narrow that the driving seat was virtually central.

-

i:

:

: as

3

:

‘ Se SEA

:

cy :

Re Ae ‘

henna ok by

C16. 917s were popular with private entrants, because with. any other cat a team was certain to bean also ran. Zitro Racing Cars, of Geneva,

used 917 025 during 1971, albeit without much success. Dominique Martin and Gérard Pillon

shared the driving at Le Mans but the car was never in the hunt, and retired when the gear selectors broke.

$

oo

C17. Team Auto Usdau was a German organisation which bought one of the two 917Ks previously owned by Steve McQueen's company,

:

: j

.:

oye

ea

Solar Productions, and used in the making of the

:

film ‘Le Mans’. Like other private teams, they had the works cars to contend with, so could not

Ney

ing

Hei

Be

eas i

N

&

;

;

expect to do especially well. At Brands Hatch Jost and Kauhsen came sixth in the Usdau car;

the team’s best result was a 4th position at Spa.

C18. David Piper entered 917 010 for the 1970

edition of the BOAC

1000km, but the engine

broke a camshaft during practice and, without a

Spare available, the car failed to make the start.

C19 & C20. Kremer Racing’s 917K81

featured a host of

aerodynamic modifications, these being the result of new knowledge acquired in the late seventies. Most noticeable are the squared-off sills and nose, the

lengthened tail and the full-width wing. At Le Mans scrutineering the car was initially rejected because it was a closed coupé, so a hole had to be cut into the roof, this being enough to satisfy the scrutineers that the car had then become open-topped! Advantage

was

taken of the cutaway roof to fit an additional rear view

mirror, as vision via the interior mirror was negligible,

the wing obscuring most of the view. Slots cut into the bodywork aft of the rear bulkhead were intended to supply more air to the engine, which it was thought was being strangled, although subsequent investigation suggested that this was not the case.

C21

(left). Manfred Kremer (left) and Bob Wollek

demonstrate the lightweight construction of the 917K81's chassis by holding it high above their heads, whilst Erwin Kremer, suitably fortified with a tot of Jagermeister, hopes they don't drop it on his.

AUTOCAR

11 May 1974

~ 1100 bhp, 240 mph Mark Donohue,

CamAm

Champion (Ret'd) talks

|

about.the birth, the life and the death of the world’s fastest racing car: the Porsche 917/30

by Ray Hutton

TOTAL DOMINATION—THE WORKS PORSCHE 917/30 OF THE PENSKE TEAM, DRIVEN BY MARK DONOHUE (INSET) WON SIX OUT OF EIGHT RACES IN THE 1973 CAN AM SERIES

“At this time there is nothing in the world any quicker, any better handling, any more advanced technically, or any more fun to drive. It is to me, the perfect race car.” These are the words of Mark Donohue, CanAm champion, and the subject of his unabashed enthusiasm, the Porsche 917/30 that he used to win the 1973 series. We were talking at Riverside, California, on the eve of his sixth win in the eight-race series. At the time I did not know that 24 hours later, when he was crowned champion, Mark was to announce his retirement from race driving. And neither of us knew until a few weeks later than the Sports Car Club of America were to change the rules of the

Canadian-American

Challenge

Cup so as to outlaw the turbocharged Porsches that had won the championship two years in a

row. With

the fuel limit (73 US

galtons) applied

for 1974 races,

the 1.S5mpg 917s will not be able to run in their present.form. The critics are pleased, pointing out that no Chevrolet-powered car could compare to the turboPorsches, and that the earlier 917/10s could not stay with the Penske-prepared 917/30, replicas of which were to be made available by Porsche for the 1974 season. It had become, they said, a race of investment. Porsche had reputedly spent over a million dollars on the CanAm _programme and Donohue’s six wins

in 1973 netted only 114,533 dollars. Even with generous sponsors, that doesn’t make sense, claim the

losers — who include some of the private Porsche teams. But let us leave aside the frightening cost of the project for a moment and consider the development of what is probably the fastest circuit racing car in history — and likely to remain so for some time. to come. It is an example of the thorough scientific approach for which Donohue — a highly qualified engineer as well as a super driver — and Roger Penske’s team are renowned. They dubbed it ‘““Penske’s Unfair Advantage”. “The reason I say this car is so good,” explains Donohue, “is that since the inception of the

project I’ve been directly involved. Nothing has been done to that car that I didn’t think was right. All the development went in directions that I wanted to go. That’s very satisfying for me — I've done something, it works, I have to live with it, and I’ve won with it. “I have developed cars before, but this was one that everybody said was impossible. Porsche didn’t agree, neither did I. I had faith in them, they had faith in me. It was a tremendous honour to go to a factory like that, and for their engineers to trust what I wanted, to see that what I wanted to do was win.”

AUTOCAR

Regulation trouble The history of the Porsche 917 is one of continuous clashes with racing’s rule-makers. The original coupé appeared at the 1969 Geneva Motor Show and it was

something of a shock to realize that the CSI’s reduction of the production qualification for the then Group 4 to 25 cars per annum had produced a new breed of super-powerful, super-expensive endurance racing cars. The 4 S-litre 917 was a big jump for Porsche, who only a year before had been racing 2.2-litre 907s. At first it didn’t handle well, and

there was a row at Le Mans when the organizers wanted the suspension-connected aerofoil flaps removed and _ Porsche claimed they were essential for the car’s stability. In due course the 540bhp 4.5-litre flat-12 engine became a full S-litre and for two years these magnificent monsters dominated the long distance sports car classics. Then for 1972, much to Porsche's disgust, the 3-litre prototype rules were reintroduced and the Porsches rendered ineligible. As early as 1969 they had built an open-bodied version of the 917 for the late Jo

Siffert to drive in the CanAm series, Outlawed from the World Championship of Makes, they decided to concentrate on these North American races in 1972 and they chose the Penske team to develop the turbocharged version jointly with the factory engineering department. Donohue recalls their original strategy: Planning perfection “We talked for a week before I even got into the car. We all agreed on a basic approach, from which we would not waver no matter who criticized — and at

11 May 1974

The drawings, published by courtesy of Auto Zeitung emphasize the length of the tail and engine bay of

the Porsche 917/30. The 5.4-litre flat-12 engine is air-cooled. It has two valves and two sparking plugs per cylinder and Bosch fuel injection. The twin turbochargers are

by Eberspacher with an Airesearch waste-gate (above the tail pipes, centre). The transmission is a Porsche 920 four-speed. There is no differential and the titanium drive-shafis have rubber ''doughnut™ joints at their inner ends. The multi-tubular chassis frame is

aluminium and weighs 133 lb

AUTOCAR

11 May 1974

Performance Racing car performance in straight-line acceleration terms is often out-of-this-world compared to even the fastest road cars Porsche put their computer to work on the theoretical acceleration of the 1972 917/10 with about 1,000 bhp. The results were 0-60mph 0-100mph

2.1 sec 3.9 sec

0-200mph

13.4 sec

The 1973 Porsche 917/30 described on these pages can be expected to be even quicker!

(Source: The Racing Porsches by Paul Frere. Published by Patrick Stephens Ltd.)

Sc

AUTOCAR

Mark Donohue | tackles a less demanding technical

problem

give

the

engine

some

power

without boost, so that it could be driven round a slow turn as if it was normally aspirated. “You

can

never

interest

an

engine guy in making an engine idle, or start properly, or run at part throttle. They’re interested in the figures on the dyno. It took a little while for me to persuade them to develop the uncharged range of the engine fit mild cams, restricted intakes and so on.” So in its final form the 917 turbo is not so very different to drive from a normally aspirated racing car. Donohue does not believe in left-foot braking, for example, to overcome the throttle lag (except at the start of a race):

the time there were a lot of people who criticized our approaches. A lot of days were wasted in fruitless experiments. But at least we went down the path, saw it was junk, and never went down there again. Other people might have said ‘we know that’s no good, why go down that road?’ We went down to see it was a dead end. To be sure.” a The development pro-

gramme

was

much

more

than

taking an existing car and making it work with a turbocharged engine. Donohue is guarded about the handling of the 917 when he originally drove it. ‘‘Let’s say that we would have done it a different way. If you really held your breath, and the track was smooth, it was fast. But Porsche had gone to better shocks (dampers), steering dampers — Band Aids. I think we showed them something else. At Atlanta I demonstrated with lap times some of our ideas. They (Porsche engineers) then improved on them and we started really working

together. As soon as that bridge was crossed we were able to get to work

on

the front, the back, the

fuel system, the aerodynamics — the whole car,” Donohue may be diffident about the improvements he made to the 917’s roadholding and handling but they were obviously considerable. Vic Elford, who was one of the faster drivers of the early 917 coupes and had one race in the factory’s turbo-917 test car last season, says that the change is remarkable and that the CanAm car is much better balanced than the coupé. ; Cutting the lag The actual production of power

from

the

turbocharged

engine

was not a problem once the increases in temperature had been coped with — by increasing the

cooler fan speed, making

valves

and pistons from special materials, and developing a new type of platinum sparking plug. But making the best use of that power and making the car drivable was another matter. Donohue knew about turbocharged engines (he won at Indianapolis in 1972 with a turbocharged Offenhauser in the Penske McLaren) but road racing with them was something new. The problem, of course, was response, the time that the turbocharger takes to build up to its 90,000rpm working speed. “Any turbocharged car has some throttle lag’ says Mark, ‘“You have to change your driving habits a little, opening the throttle before you want the power. But we have worked really hard to reduce that lag. Now it is between a half and a tenth of a second, depending on rpm. If the motor is running at 5,000rpm and you open the throttle it takes .. . no I don’t want to tell you that .. . let’s say it takes x. At 6,000 rpm it takes '/2x. So you gear carefully. It has good power from 5,000 — 8,000 and you can get boost at 4,500. In fact, generally we use the 5,500 to 8,000

range.

We

shift

at

7,800

tpm. The rev limiter is set at 8,300, but 8,500 would be possible. The trouble is that at 8,500 and three quarters with one weak valve spring, a valve can hit a piston — that valve train is very light.” The throttle lag problem has been attacked by sophisticated flap valve systems which release back pressure in the induction manifolds and permit turbocharger speeds to be kept up while the engine breathes “normally” at low speeds. Porsche are tightlipped about the details of this but Donohue regards this part of the development as critical. “There are times when you cannot anticipate when you need the power. We worked a long time to

11 May 1974

engine is very reliable in its latest form and have used this as a counter to those who criticize the high (70,000 dollars?) initial cost. The 1973 5.4-litre engine was apparently a big improvement on the previous year’s S5-litre. It could rev higher thanks to different cam timing, new camshafts, revised injection calibration and blower arrangements. “The package is now so perfect that anybody can get 800 miles (two races and practice) of trouble-free service. It’s because Porsche have

such excellence of thinking,” says Donohue. The Vasek Polak and Bobby Rinzler teams that ran 917/10s last year might not entirely agree, however. With the turbochargers set to

—

Champion's seat. Gauges on the left are for turbo boost and fuel pressure; switches above them for four separate ignition systems and

two fuel pumps. Dials flanking revs counter show oil pressure and

temperature

“In the Porsche the left foot is for working the clutch. It is very critical, if you miss a shift you can do a lot of damage. I'd get confused if I kept switching.” In this respect the driving technique is entirely different fron Indianapolis: “In any Indy car you: don’t need response. You hardly get out of the blower at all, the engine hardly ever backs off. But the engines are unreliable, very sensitive; you never know when they are going to go. It’s kinda like driving a hand grenade.” By comparison, Donohue and Penske claim that the Porsche

Sax

deliver 1.3atm. boost, the 5.4 litre engine gives about 1,100bhp, over 100bhp more than the 1972 5litre. Increasing the power further is as simple as turning the screw on the blow-off valve on the cross pipe between the two turbochargers, and several of the Porsches in last year’s CanAm had devices to allow the driver to increase boost from the cockpit. “I used mine only once, at the end of a race,” says Donohue. It is estimated that the increased boost — to 1.7atm. — gave more than 1,200bhp. (At 2.2atm. on the test bed a figure of 1,560bhp has been recorded!) To some extent this is a progress to diminishing returns, for very high boosts increase piston blow-by which can pressurize the crankcase and reduce power,

while

tremendously

temperatures

and

there

rise

is the

danger of detonation, which with

a petrol-burning engine difficult to deal with.

is very

AUTOCAR

11 May 1974

Too much power? Is this really going too far? Have these cars got too much power, more than they can ever use? Donohue answers that emphatically: “Too much power is defined as when at the end of the straight in top gear the wheels are still spinning, the driver can’t cope. We are way, way away from that. We estimated how much power was needed to do that with an aerodynamically loaded car — 2,400bhp. Then you would truly need a very talented driver to hold that car all the way down the straightaway. Can you imagine what a thrill that would be? I'm a horsepower freak.” Having done the initial development of the car in 1972 Donohue had a crash at Road Atlanta and missed four races; George Follmer, brought in to take his place, won the CanAm Championship. The 917/10 was clearly much faster than anything else by the end of the season. Why build another new car? “The 1972 car was a compromise, we ran out of time. It was a good car, but sensitive, critical to the axis between balance and performance. We wanted a car that was more level. “We redesigned the basics, changed everything. We lengthened the wheelbase — primarily to get more fuel in the middle. Porsche were typically thorough.

Porsche engineer Helmut Flegl looks on as mechanics work on the 917/30. With engine specialist Valentin Schaefer he was in charge of the development of the CanAm car from the factory end

showed

promise

speed

immediately

— the maximum

jumped

to

240mph!

‘Mark Donohue’ wants to lengthen the wheelbase — how much?’ Nobody is smart enough to know how much, so they built an adjustable chassis.” News of this chassis — a three piece tubular frame with three different centre sections of different lengths and located by eight bolts — prompted the opposition to think that Penske’s team would be using different wheelbase cars for different circuits. In fact they settled on the longest at 97in., 6.5in. more than the previous car. With the long wheelbase

came

the long tailed body, 22in.

longer than years racing

the 917/10. “For cars have had a

terminal speed of between 212 214mph. Indy cars went that fast in 1968 and they still do. The 917/10 did the same. Only two other cars have gone quicker. The 917/30 reflects recognition of that

problem,’ Donohue — explains intriguingly. “We are testing in France at Paul Ricard, a circuit with a long

o

e- Se a

“Log” inlet manifolds above each bank of cylinders are fed by

turbochargers at the rear, conceal a clever valve system. Note twin distributors and transmission oil cooler, engine oil is cooled from Jront-mounted radiator

straight. The weather was bad, and things were going wrong. Over a few drinks one night I said to Helmut Flegl (Porsche chassis engineer),

‘All

cars

are

“The lap times weren't faster; we were giving away the extra speed by loss of balance. But at that point we had to make a decision — do we go long-tail or not? Porsche weren't keen, they said that there are not many fast tracks in America. But I said that it was the only thing that made any sense to me from an engineering standpoint. Id live with it no matter what.” The tail was developed, styled and wind-tunnel tested to give an entirely new body shape. But Donohue didn’t have a chance

to demonstrate

the

917/

30’s fantastic straight line speed during the season.

The only op-

portunity should have been at the final race at Riverside, but the organizers decided to use the shorter, twistier infield circuit instead of the 3.27 mile full track with its long straight. “I’m so disappointed,” said Mark.

doing

214mph, which cars are quicker? Two — the 600bhp long-tailed Le Mans 917 coupe and the 485bhp Ford Mark IV. What’s the difference between those cars and ours? Only one thing — their long tails. And who is more talented at making long-tailed cars than Porsche?’ “Fleg] wasn’t enthusiastic — he said it was difficult to make them work properly. So we had a few more drinks and I persuaded him to give it a try. The next day they built one from an old tail with ally sheet and tubing. It was quite wrong to start with but it

Other novelties There is more to the 917/30 story than this. The car has, for example, no differential, despite its 19in. wide tyres. For the last race of the season it had the rear anti-roll bar hydraulically adjustable from the cockpit. The team admit to a few failures — bearings at drive shafts, the carrier for the diff. that isnt — but none with the tubular frame which most designers would now regard as old fashioned. Like the coupes of a few years back it is gas pressurized so that any cracks can be detected by a simple gauge check — and it is made of aluminium.

Donohue sium

The

frame

quiring

917/10

crashed

that

had a magne-

(He joked

journalists

that

with

en-

it was

“unobtanium’’) which saved 40lb in weight but doubled the cost. Now costs have become a primary reason for the 5.4-litre turbo

917/30

being

banned.

Donohue had little sympathy for the changes. “Five years ago we suggested a 7-litre stock block/5litre racing engine formula and it was rejected. We got out of the CanAm as we couldn’t be competitive. Now we have come to the fight with the sharpest knife and everyone is bitching at us.” He doesn’t like the sound of the move towards 5-litre and 3-litre engines for 1975. “All the thrill has gone for me at that point.” There is something appropriate about Mark Donohue. CanAm Champion, and some say a potential World Champion, retiring from racing when his “‘perfect race car” had reached the end of the line.

zg

In late 1967, the maximum permitted engine size for the World Manufacturers’ Championship races was set at 3 litres for prototypes and 5 litres for ‘sports cars’ of which at least 25 examples had been built. At that time, only the

Ford that

GT40

and

category,

the Lola-Chevrolet whilst

Porsche

were

and

Ferrari

homologated were

in

designing

prototypes whose favourable power-weight ratios all owed them to think that they would be generally more competitive than the ‘sports cars’ with American pushrod engines

Nevertheless, as we have already had occasion to note, this balance between ‘sports’ and prototypes was only a temporary situation. Until it fell apart, it did in fact suffice, but it was obviously a decision loaded with possibilities, notably that, if finance allowed, a builder could launch a programme to construct 25 6-litre prototypes which, thanks to homologation, would become ‘sports cars’. This escaped neither Porsche nor Ferrari, but whilst the Italian manufacturer could only protest and denounce the absurdity of the rule, the

German

company,

in

the

throes

of developing

a 3-litre

prototype, commenced the design of its future sports car which would be presented for the first time in public at the

Geneva

Salon,

in March,

1969.

In June,

two works

917s

of 4.5 litres lined up at the Le Mans 24-hours and outclassed the opposition before retiring with mechanical

failure. Nevertheless, a few months later a 917 triumphed in the 1969 Austrian Grand Prix at Zeltweg, its first major

TEST: PORSCHE 917

international victory. That season, 917s won at Daytona, Brands Hatch, Sebring and Francorchamps before giving Porsche its most coveted victory, which the company wanted to obtain at all costs: Le Mans

The

day after the

opportunity car which

of driving is in almost

Nurburgring the Gesipa every

1000 Racing

respect

km,

| had

Team's

the same

917,

the a

as the one

by

which was driven at Le Mans by Hans Herrmann and Richard Attwood. Before going any further, | must give my warm thanks to M H G Biermann, who sponsors the Gesipa Team named after his company, a major manufacturer of rivets — and his driver Jurgen Neuhaus, who sportingly made this test possible

Jose

Principle Features

Rosinski

In principle, one could think that the need to homologate a model

would

prevent

its

evolution.

In

reality,

it does

nothing of the sort, thanks to the various ‘extensions’ and

the car which won le mans in 1970

‘normal evolutions of the type’ which allow the makers gradually to bring in practically all the modifications which they consider necessary to make to the original model. Each race brings its quota of new experiences, and it is perfectly well understood that a competition car must progress rapidly, although it has to be said in this respect that the famous homologation papers are only red tape with which the manufacturers and the International Sporting Commission play games with each other. It is enough to attend at race scrutineering to realise that the

task of the technical inspectors charged with checking the conformity of the cars with the paperwork in question is almost impossible to accomplish in the normal time allowed if they want to get to the bottom of things. Consequently, this rule is in fact only a fastidious masquerade, and in truth everyone must be delighted at its abolition for the 1972 season!

4

ak

When

the 917 appeared, it resembled a big 908 from all

points of view except one: the front/rear proportions were considerably altered in favour of the front. In fact, a desire to keep overall dimensions compact, combined with the adoption of a long, cumbersome 12-cylinder engine, led Porsche's designers to move the driving position noticea bly forward. This was strongly criticised at first, some people stating peremptorily that driving the 917 would be made very sensitive because of it. We now know that since then, Porsche have gone much further in this direction with the 908/3, with total success. The chassis of the 917 is a spaceframe which is different in that the tubes making it up are in a special alloy, which at the same time is very light and provides the required rigidity. Also worthy of note are the gussets reinforcing the structure at the tube joints. The suspension is of classic layout, and the brakes, fitted inside the wheels, consist of ventilated discs and of calipers by ATE for

customer cars, like the one we tested, or Girling in the case of the works cars; this is the first important change to note. Since 1969, the centre-lock magnesium wheels have grown in width, having gone from 9 inches to 10 inches at the front, and from 12 inches to 15 inches at the rear. But the most obvious change concerns the bodywork, of which in fact only the central part is unchanged. The front has been slightly modified, it now being more blunt, whilst the rear has undergone a radical reshaping, with the aerodynamic long tail being abandoned in favour of a much less delicate shape, shorter by 50cm, which entirely uncovers the rear part of the car. In fact, the first 917s showed themselves to be very difficult to drive, not because of construction, but due to aerodynamics. The car was unstable at high speed, through lack of downforce, and it was only possible to correct this by fitting this new tail, which is, however, much less effective in terms of

drag. Since then, at Le Mans 1970, we saw a new long tail which is better designed than the first. and which allows a maximum speed in excess of 223mph, whilst the short tail version could

not exceed

205mph,

in both cases with the

5-litre engine. It was not that engine which was fitted to the Gesipa Racing Team car, any more than it was to the Le Mans winner, but rather the 4,494cc version. The unit is a flat-12, air-cooled, of 85mm bore and 66mm stroke. The crankcase is in magnesium alloy, the cylinders in chromealuminium, and the heads in light alloy, The forged steel crankshaft turns on eight main bearings, whilst the rods are in titanium. The two valves per cylinder are operated by

four camshafts. two per cylinder bank, operated by gear clusters. Fuel is supplied by means of a Bosch pump with twelve injectors, itself fed by three electrical pumps

drawing the fuel from the lateral tanks which contain the 120 litres permitted by the regulations. Lubrication is by dry sump, and the very significant quantity of oil in circulation (35 litres) leads one to think that the lubricant takes part in the cooling of the engine. whose fan is installed horizontally; the blower is driven by a layshaft running above the crankshaft. Finally, the ignition is double and transistorised. Born with 520bhp at 8,000rpm, and 46mkg at 6,800rpm, this imposing engine now develops 560bhp at 8,300rpm, the torque of 50mkg still

being at 6,800rpm. A multi-plate dry clutch links up with a four-speed synchromesh transaxle. On its début, the 917 had five speeds, but that gearbox was abandoned this year, as it has suffered its share of difficulties. Two massive halfshafts with double universals transmit the power to the rear wheels. And now we come to the 917’s trump card: its

lightness. Announced at 896kg at birth (in long-tail form) it has now reached the lower weight limit allowed by the rules, 800kg, this constituting a considerable advantage over the 512S which weighs nearly 100kg more!

On the Track was discovering not only the 917, but also the South oop of the Nurburgring, much shorter than, but certainly as difficult as, the big 14-mile circuit, fast, just as narrow, and above all extremely bumpy, one half consisting of a ong descent, the other being an equivalent climb. Fortunately,

Rolf Stommelen

was there setting up his F2,

and he was willing to give me three laps to show me the ines, the braking points, and the main traps to avoid. On board the 917, | listened to the advice of Jurgen Neuhaus: don't exceed 8,000rpm — the maximum allowed in racing is 8,400rpm — don't use first except for starting (a sliding stop on the gear lever has to be moved to get it into irst) and, finally, keep a tight hold on the wheel over the bumps: Then he closed the door, and | started the engine. It emitted a deeper sound, less strident and less harsh, than the Ferrari 512S. Throttle response seemed less prompt, but this is perhaps only an impression due to the

characteristic

jerkiness

of the

mechanical

tachometer’s

needle. On the other hand, the pedals are very soft, with an agreeably progressive action. | had some trouble getting first, but once located, | had no trouble making a careful start under the slightly worried gaze of Neuhaus and his mechanic ... | moved quickly into second to take the tight

At the Wheel The 917, a closed ‘coupé, is only 36 inches high! This means that getting in is hardly easy, particularly since the wide door sills, which form the top of the fuel tank containers, are very high. However, this problem is common to nearly all closed competition cars, maximum accommodation not having being sought by the designers, who evidently prefer to reduce the size of the cockpit as much as possible. One slides one’s legs under the wheel as best one can, to find oneself almost prone in a bucket seat of unusual shape, its cushion being longer than its back support. The position thus dictated is very comfortable, since the body is well supported laterally, and very little strain is exerted on the back. With the door closed, there is hardly any gap between it and the top of your helmet, but just enough, however, for it not to cause any discomfort. The small diameter steering wheel is placed at an ideal distance, and the pedal assembly will suit even the longest legs. Drivers of virtually any size will be able to fit behind the controls of the 917, and the Porsche's driving position is much more accommodating than that of the Ferrari 512S, although the dimensions of the two cars are similar. Making up the dashboard are three dials, inset under a long cowling in the area framed by the wheel: a big mechanical tachometer, calibrated to 10,000rpm, flanked by oil pressure and temperature gauges. No attempt has been made to smarten up or beautify this cockpit, which sacrifices everything to the quest for minimum weight, and the whole thing gives a distressing impression of confusion: clearly visible chassis tubes, electrical equipment, roughly cast steering -column support, gaping holes cut out of ventilation trunking, scruffy anti-reflective coatings It could be quite depressing if one forgot that the 917 is a car made specifically for racing, so striking is the contrast between the well-made bodywork and this ugly enclosed environ-

" ment. Apart from the instruments mentioned above, also found under the cowling are several warning lamps — notably oil and fuel pressure, and brakes — whilst various switches and controls are grouped together on a panel

facing the so-called ‘passenger seat’.

esses at low speed, getting the feel of the steering, which straightaway appeared soft and super-precise, but subject to the reactions which Neuhaus had foreseen, then the brakes, under the action of which the front tended to dive more than | would have expected. The gear lever had quite a long travel, relatively precise, which did not favour gentle changes. Compared with the Ferrari 512S’s engine, the 917’s appeared less powerful low down, but believe me, that is a rélatively academic observation, which no doubt will have some importance for Siffert, Rodriguez and company, but is of oh-so-limited interest for your humble servant ... who, | can assure you, found on those damned bumps of the Sudschleife that there was more than enough under his right foot! After some ultracautious reconnaissance laps, | stopped to adjust the mirror and also to think over my first impressions. It is not necessary to drive for a long period to become accus-

tomed to a car or a Circuit, in tune with both of them; on the contrary, it is a good idea to have a brief pause, from which one notices, on restarting, that a process of assimilation has operated — | find | can adopt a higher rhythm. | take care of my lines, tightening the line into a downhill S, but then put my right front wheel over the kerb when | was sure | had placed it right on the edge of the track ... obviously, the rear wheel follows, and since | am accelerating, it starts to slide wildly when it gets on to the damp grass. Instantly | lift off, steer into it, and the beginnings of a spin stop at once. Oof, that was close! | had provoked it by aiming wrongly, due to the unusual forward driving position, to which | am evidently not yet

accustomed. On the other hand, this little incident allowed me to confirm the 917’s exceptional controllability, thanks to the steering’s speed of reaction, and also to its high gearing — less than two turns lock-to-lock.

As for the vehicle's handling in normal circumstances, | was enthusiastic about all areas except the brakes. The suspension is quite supple, and if the wheel is held firmly

the bumps are absorbed without the 917 deviating an inch from the line chosen for it. Nevertheless, it requires more attention than the Ferrari, for it seems less stable; on the other hand, it proved physically less tiring to drive. In its favour, its balance is neutral, at least if you do not deliberately provoke rear-wheel breakaway, which is

hardly an achievement since there is all you need to do it. under your foot! When this happens, control of the slide is admirably precise, even if the gfound is uneven, provided that it is dry. In fact, | was very conscious of the fact that to tame

such

enormous

power

on

a damp

track requires

the

delicacy, skill and coolness which are the attributes of only a handful of great drivers. For those who, like me, are not so gifted, the important thing is to persuade oneself that an egg has been placed between foot and accelerator, and the game consists of not breaking it ...Accepting this, one is able to take advantage of the tractability of the engine, which. responds without difficulty from some 3,500rpm to 4,000 rpm, and of the exceptional length of the intermediates: geared for the Nurburgring the Gesipa 917's gearbox allows 92mph in first, 119mph in second, and 154mph in third at 8.400rpm! In other words, if you are not excessively ambitious,

you will not need to embarrass

yourself with too many

gearchanges,

apply

to holding

all your

attention

and will be able to the wheel

with

both

hands. Finally, it was most

problems.

the braking which presented me with First, it was never possible to brake when

the rear suspension risked being lifted when going over a bump: the rear wheels will then lock immediately. Also, under strong deceleration, the car tended to wander in a way | found quite worrying. But, we discovered later that the rear suspension was badly adjusted, which must have. if not caused, at least aggravated the phenomenon.

Conclusion Testing this fabulous car was able to confirm what all sensible people already knew: only drivers who are professional, well-trained and at the peak of their form are able to take advantage of such a machine without endangering either themselves or others on the track with them. In the face of this evidence, the incompetence of the sporting rule-makers is stupifying, for by the 25-off rule they have practically obliged constructors to sell cars which they ought to keep for their own drivers, or for such experienced privateers as Neuhaus. Happily, if one can. alas, put it that way, the accident which befell the unfortunate Woolfe at Le Mans last year has made the manufacturers more careful than the CSI, and Porsche will only agree to sell 917s to those drivers whose records and experience provide the necessary guarantees. To put the problem into perspective, | would say that on a circuit like the Nurburgring, an average driver with a conventional 908 will certainly beat the time he would be able to set at the wheel of a 917 by at least 30 to 40 seconds, if not more. Certainly, driving a 917 gently is an absolutely intoxicating sensation, but even if one does not go flat out it requires exhausting concentration. This is not because of any faults in the handling of the car, but is due simply to the performance it can attain. And as for getting the maximum from it, it has been proved that, on a circuit as

demanding

as the Nurburgring,

even

the greatest drivers

have some difficulties at the wheel, since they all chose to drive the 908/3 in the 1000km; they could go a little faster and, moreover, they could sustain their rhythm for longer. Despite terrific progress in chassis, suspension and tyres, a

car powered by an engine developing over 500bhp, and weighing a littie more than 800kg, remains an equations which is very difficult to translate in terms of driving. At all events, what Porsche's engineers have managed to create in this way is quite extraordinary, and one can only admire their success after one has had the extreme pleasure of being able to get behind the wheel of such a master card [ll

David Piper has been a staunch supporter of sports car racing since the early nineteen-fifties, and a decade /ater was one of the most ambitious of privateers, racing his stable of Ferraris which included a 250 GTO, 250 LM, a P2/3 and even a P4. He still has the 917 which he bought in 1969, and races it in the Super Sports series of which he is one of the principal members. JSA: Quite a few people were surprised when you, a man famed for his exploits with Ferraris, chose to buy a Porsche in 1969. Why did you go for the 917? DP. \ had, in fact, hoped to get a Ferrari 512S in time to get some development work done on it before the Kyalami 9-hours in 1969, and it was intended that | should be involved with the initial setting up of that car. Unfortunately, its progress was delayed, and it wasn’t ready until early 1970. My P4 was a couple of years old by 1969, and was beginning to be outclassed, so | went ahead and bought a 917, which was eligible to be used in championship races, unlike the P4. JSA: You had already had some experience of the 917, | believe? DP: Yes, | had driven a works car at the Nurburgring. What an event that was! | wasn’t at home when

the call came through from

Germany that Porsche wanted me to drive the 917, so my wife, who took the call, naturally said that | would take the drive. She contacted Frank Gardner, who also agreed to do it, so the pair of us then flew out to Germany. Despite not getting to our hotel until after midnight, we had to be out at the circuit by about 5am, for some practising before the race. The Porsche drivers, all of whom had refused to drive the car, watched as Frank and | drove it. We weren't even warned what it would be like! It really was awful, the handling being terrible, virtually unpredictable. However, we kept it on the road, and managed to make it last to the end. Porsche were delighted with us, and we received an excellent bonus — the pay was really good! JSA: You were one of the first private entrants to run a 917? DP: That's right. | was partly responsible for the design of the new tail which became standard on the 917. At Kyalami we had run my car with the tail modified on top with a raised section much like the final shape.

>=

Thy

:

——aa/* See

JSA: It is nice to see that you still run your original 917, and that the car is still in racing trim. Do you find any problem in obtaining spares? DP. Yes, spares are difficult to obtain, but fortunately | rarely need to get any. You see, | have an extensive stock of spare parts already, and many other parts | can make myself. I've made body

| moulds, so new fibreglass is no problem; | have suspension parts, i

engine parts, a full set of gears and so on, so really the only items which could cause difficulty are the gearbox casing and the engine as a whole. The gearbox casings are made from some strange alloy that’s impossible to weld, so when one cracks you have to get a new one, and that can be difficult. Complete engines are in VERY short supply — the one in my car cost a fortune — and anyone who has one is likely to want it keep it himself. However, | do have quite a lot of engine spares — crankcase, cylinders, heads — and | need little more than pistons and rods to enable me to make a complete unit. | shall probably do that soon. In fact, | have very nearly enough spares. to enable me to build an entire car, and that is a project which | shall be starting on in the near future. JSA: Did the car have any particular weaknesses during its racing career? DP. Apart from the gearbox casings, which I’ve mentioned, one problem area concerned the crankcase. This too could easily crack, but fortunately it could be welded up. | remember that we had a crankcase go during practice for the Kyalami 9-hours in 1969, and just could not get a replacement, no matter how we tried. Eventually we welded it together, using a piece of McLaren wheel to cover the crack. Nobody would believe that it would work, but it held together and Dickie Attwood and | won the race! JSA: Have you made many modifications to your car? DP: Yes, all sorts of things. The nose is now detachable, unlike the original which was bonded to the chassis. The Porsche people were horrified when they saw what | had done, but it’s a modification which | have made to most of my cars — the LM and the P4 for example — and it provides far better accessibility than before, with no drawbacks. You will have noticed that most modern sports racing cars have fully detachable 35

noses. The car's fuel capacity has also been increased, with an extra tank on the offside, alongside the engine, and a bigger reserve supply on the left. That was done for Can-Am racing, where there was no fuel capacity limit and you had to try to avoid making a fuel stop during a 200 mile race. There are other things, as well; the engine is a 5.4-litre, which had originally been turbocharged, and has shown over 600bhp when under test. The undertray is aluminium, not the usual fibreglass, the seats are different and so on; you often find that when a racing car is a few years old there is not a lot of the original car remaining. JSA: Bearing in mind your original experience of the car at the Nurburgring, how do you rate the car's drivability now? DP: \t's now a different car, fully sorted and really quite easy to handle. There is plenty of torque, and the car is very tractable. Even so, | only allow it to be driven by people who are familiar with 917s because of the possibility of engine damage.

36

JSA: 917s were prone to engine damage if over-revved, weren't they, because the rev-limiter didn't work fast enough? DP: Yes, the problem was caused by the tappet which could break up if a piston met a valve. The bits of tappet would then go right round the engine and cause all sorts of damage. JSA: The driving position of the 917 used to come in for some criticism, because it was so far forward. DP: That is something you can soon get used to. The cockpit Is very narrow, Porsche building it right to the limit of the rules. When Mike Parkes built the Ferrari 512F for Filipinetti, he made the cockpit much narrower than usual, and brought it down to the same width as a 917; | then supplied him with a 917 windscreen which went on to the Ferrari!

JSA: Do you use the car very much nowadays? DP: Not really, | suppose. | had it out at the Motor 100 at. Silverstone, and that was its first outing since the Freeport race last year. However, it should see some racing in the Super Sports series later this year, and | hope to take it out to a race in Malaysia. The series has proved very popular all over the world, but keeping cars like the 917 in racing trim for these events is very expensive; we couldn't manage without the support that we get from Lee Cooper, our sponsors.

Gloucestershire, GL54 3HG, the Porsche Club of America, 1753 Las Galinas, San Rafael, California 84893 and the Porsche Owners Club, Inc. The last organisation, which celebrated its 30th anniversary in 1985, publishes a bi-monthly 32-page professionally-printed newsletter, and arranges various competitive events for Porsche drivers. Their headquarters can be contacted via P.O. Box 7293, Van Nuys, California 91409-7293.

Clubs With only about 45 917s surviving throughout the world, it will come as no surprise to learn that there is no such thing as a 917 Owners’ Club. Most people who own one of these super-exclusive cars seem to be aware of the whereabouts of all other owners within a substantial radius of each other, and so know exactly whom to contact when assistance and information is required. The very nature of the 917, like most other out-and-out sports-racing cars,

instils in the type’s owners a willingness to get involved in do-it-yourself to a far greater degree than with more mundane vehicles. A 917 owner would not expect to wander into his local Porsche dealers and obtain a replacement windscreen over the counter, nor would he telephone the Secretary of the Porsche Owners’ Club to ask which of half-a-dozen stockists is likely to quote the lowest price on a new crankshaft. If, however, he does wish to meet up with others who share his passion for Porsches, albeit ‘ordinary’ 911s and 930s, he can join one of several clubs. In the English-speaking countries the best known clubs are the Porsche Club of Great Britain, Ayton House, West End, Northleach, —

Specialists People who specialise in the repair and maintenance of Porsche 917s are also rare indeed, but there are a few who have amassed years of experience which now make them fully qualified to tackle any work on this daunting vehicle. Needless to say, the Porsche company itself knows a thing or two about the 917, and recently a new department has been set up to provide restoration work on any kind of Porsche, including, of course, the fabulous flat-12. Porsche's standards have always been high, and they are unwilling to tackle anything less than a total mechanical or body rebuild. They can be contacted at Dr.Ing.h.c.F.Porsche AG, Postfach 40-06-40, Porschestrasse 42, 7000 Stuttgart-40. Anyone who goes to the trouble of building a 917 from scratch will learn much about the car in the process, and happily the + Kremer Brothers are willing to use their knowledge to assist their i

=

customers. Kremers have been remarkably successful with their competition Porsches, and since 1968 have won the Porsche Cup eight times, have scored numerous wins in sports car races, and even won the Le Mans 24-hours, a superb achievement for a private team. They are prepared to undertake any work on the 917, from minor jobs up to complete rebuilds, and are versatile enough to have tackled Ferraris, Maseratis and Cobras as well as the more usual Porsches. E & M Kremer GmbH can be found at Robert-Perthel-Strasse 31, 5000 Koln 60, Germany.

In Britain, David Piper has to be THE Porsche 917 expert. Having raced the cars continually from 1969, there is little he does not know about them, and less that he cannot fix. Although he rarely restores or repairs cars for others, he is willing to provide spares to keep other 917s on the track. His address is Rosedene House, London Road, Windlesham, Surrey. In the USA, the name most associated with Porsche 917s is Vasek Polak, who operates a Porsche dealership from 199 Pacific Coast Highway, Hermosa Beach, California 90254. From his days as entrant of Milt Minter’s Can-Am 917PA, at least six examples of the type have passed through his hands, and his experience of the car is obviously considerable. An interesting project is currently underway in Australia, where the last 917/30 is being built up. This car, chassis number 917/30 004, was not completed by Porsche, being sold as a chassis/body unit. All required mechanical parts now having been obtained, Porsche Cars Australia, Pty, P.O. Box 368, Noble Park, Victoria 3174, are doing the work. No doubt it will stand them in good stead should anyone else in Australia (two other 917s are there) need assistance with their cars. 37

Books The 917 was an exciting car, and a successful one, so it is not surprising that many references to it have appeared in print. At one time several books dealing solely with the 917 were available, but most of them have long since disappeared from the publisher's catalogues. The most recent work covering the 917 is Porsche 917 by Michael Cotton (Kimberleys, 1986) an inexpensive general history of the car. The Making of a Winner; The Porsche 917 by Larry Pihera (Lippincott, 1972) contains a fascinating facsimile of the pre-race checklist used by the works. Cars in Profile No 5: The Porsche 917 by Paul Frére (Profile, 1973) benefited from Frére’s close connections with Porsche to become a mine of information. The best illustrated study of the 917 is undoubtedly The Fabulous Porsche 917 by Peter Hinsdale (Thompson, 1972), wherein every change in shape is recorded. Apart from the books which have the 917 as their central theme, there are many other volumes which provide useful reference to Porsche's masterpiece.

38

Porsches at Le Mans by Dominique Pascal (Haynes, 1985) illustrates every Porsche which has raced at the French circuit, so naturally the 917 is well represented. Porsche — Double World Champions 1900-1977 by Richard von Frankenburg with Michael Cotton (Haynes, 1977) covers the car's racing history, as does Anthony Pritchard's detailed review of the 1968 to 1971 racing seasons, Sports Car Championship (Hale, 1972). Paul Frére’s links with the works

are nowhere more apparent than in his two books The Racing Porsches Patrick Stephens /Arco, 1973) and Porsche

Racing Cars of the 70s (Patrick Stephens, 1980), both works giving an unrivalled insight into the manner in which Porsche developed and honed their cars. John Wyer’s splendid autobiography The Certain Sound (Haynes/Edita, 1981) is required reading for all sports car

enthusiasts; Wyer’s droll account of his two years with the Gulf 917s is not to be missed. The Gulf-Porsche years are seen from a different viewpoint in Racing Mechanic, by Jeremy Walton (Osprey, 1980) an amusing biography of Gulf’s chief mechanic, Ermanno Cuoghi. From Porsche-Carrera 6 to 962 by lan Bamsey (Tenorhart, 1985) puts the 917 in perspective by dealing with all of Porsche’s greatest sports-racers. The Porsche Book by Jurgen Barth and Lothar Boschen (Patrick Stephens, 1978) uses works sources to detail every Porsche variant in its near 500 pages.

1 1. David Piper's first outing in a 917 was in this

2. 917 010 was the first 917 to be run by Piper as a

short-tail coupé at the Nurburgring in 1969. The car

private entrant, seeing service in the Americas, the Far

was in as-built configuration, with side exhausts and

East, Africa and, of course, Europe. It is seen here at

with adjustable flaps on the tail. An 8th place finish was

Kyalami, when taking part in the 9-hour race held in

considered quite good enough on the tortuous ‘Ring,

November

where the driving was shared with Frank Gardner. 917

modified tail, incorporating a raised fender line and a

004 was /ater rebuilt to standard 917K specification,

full-width spoiler, much of the design being carried over

and saw service with JW Automotive Engineering.

into the later definitive tail.

1969. The car was being tried with a

3. The chassis frame of the 917 was a masterpiece of strong, light construction.

The example shown here is

4. Two engines were at the disposal of the Kremer team during 1981. On the left is a 4.5-litre unit, that on the

the frame which went into the Kremer Racing 917K81,

right being of 4.9 litres. Externally the two versions are

and which weighed in at a mere 54kg. At that weight it

virtually identical, although the two engines seen here

was some 7kg heavier than the Porsche original, the

were actually painted in differing colours. The flat-12

difference being due to the substantial supports for the

was a very wide engine, but had the advantage of being

roll-over bar, and the provision of compressed-air jacks

lower than a V-12. Surprisingly, in view of its bulk,

at both front and rear. In the background of this picture

there was never any problem in keeping the engine

can be seen a new aluminium mould for one of the sill

cooled, the fan always proving quite adequate, even in

panels.

the engine's final 1,100bhp form.

5 5. Five-spoke centre-lock Porsche wheels were cast in magnesium, and were usually painted an uninspiring

semi-matt black on cars destined for racing. The design remained unchanged throughout the 917’s career.

6 6. This was the extraordinary sight which greeted the CSIs representative when he arrived at the Porsche factory to check on the company’s claim that they had built no less than 25 examples of the 917. They proved

that they had done just that, but were not very happy at being required to do so; most of the cars had been hastily assembled purely for the purpose of obtaining homologation, and were subsequently taken apart then rebuilt when required. /t says a great deal for the efficiency of Porsche’s methods that they were able to

provide the full 25 cars only 10 months after the project

was begun under the design leadership of Hans Mezger.

7 & &. The ingenious detachable long tail was a most original solution to the perennial problem of shaping a car for it to be suited to both long and short tracks.

With long tail installed the car's drag co-efficient was reduced by about 17'/2 per cent but it suffered a loss of downforce which made it particularly difficult to handle.

The so-called ‘\angheck’ was intended mainly

for Le Mans, where its low-drag shape could be put to

good use on the Mulsanne Straight, the car reportedly reaching a top speed of 236mph!

41

12 9 & 10. Both versions of the tail featured twin winglets

13. This photograph illustrates well the cockpit as

which were operated automatically by suspension

described in José Rosinski's track test, included in this

movement, the winglets changing angle of incidence to

book. On the vertical panel can be seen the four ignition

help compensate for changes in the car's attitude.

cut-outs, each dealing with three cylinders, then the knurled knob which operates the windscreen wipers and washers, and the ignition switch with key in place. The lower row contains the fuel pump warning light, twin

11 & 12. Entry to the narrow cockpit is via inordinately wide sills, which do not help in the haste of a Le Mans start. Accommodation can best be described as claustrophobic, but the seat gives excellent support. The passenger seat pays lip-service to the regulations which require sports cars to be 2-seaters, but it is virtually

connected switches for the fuel pumps and the light switch. Atop the dashboard are the plunger to operate

the fire extinguisher, and the main ignition cut-out. Angled towards the driver is the toggle switch for the

cooling seat, nowadays not used on this car,

917 010.

useless; however, there are not many occasions when someone is given a lift in a 917, so complaints are few. Note that the battery resides immediately behind the

14. Cockpit air is taken out through opening

passenger seat; in this instance a FIAMM unit is

side-windows,

installed, but most 917s were originally supplied with

pressure from inside, there being no system for propping

Letta batteries.

them open.

42

which are kept open merely by air

15 15. The original langheck body shape is shown to

76. Langheck

perfection in this view of a 1969 car, decked out in Gulf

agreed that he would use, following his rejection of the

7977 style — the type which John

Wyer

livery, although the 917 never raced in this

1970 type, which was thought to have given away too

configuration for the Gulf-JW team. Wheels had

much in terms of handling in its quest for low drag: This

polished rims, the centres being bright orange,

car is the Siffert/Bell Le Mans entry, 917 045, which

considerably improving the car's overall appearance.

suffered first a failed rear hub bearing, then a cracked

Unfortunately, when JW’s cars finally reached the track

crankcase which put it out of the race.

they wore the usual dirty black wheels.

this, the final version of the \|angheck, with the original

Comparison of

7969 type shows that the exhausts have been relocated from the rear of the sills, the plexiglass rear window has been removed, the rear fins reshaped, movable flaps

removed, rear wheels partially faired in, and nose panelling squared off.

te beee

r

43

17 17. This interim

1970-type \langheck has a tail very

similar to the later version, but without the wheel spats.

718 & 19. In the period from 1969 to 1973 Porsche learnt — and taught the world — a great deal about aerodynamics.

The changing shape of the front of the

917 \angheck shows how the car became much /ess

visibly sleek by 1971, the bluff front of the /ater car

permitting less air to go underneath, thus reducing both lift and drag. The body of the 1971 version was widened to cover the new tyres which were then

coming into use, although the front canard fins of the 1969 model meant that the earlier car had an overall width very nearly as great.

44

20. The upper nose surfaces of the 1971 \angheck were concave, the shape proving especially effective in providing downforce.

This particular car, 917 045, was

eventually repainted in Martini colours, so as to resemble the Elford/Larrousse Le Mans car, and in that

form it was loaned to the Musée de ‘Automobile at Le Mans.

21. David Piper's 917 010 displays the definitive shape of the coupé as raced during 1970 and 1971.

The tail

features the deeper rear fender line which leaves a pronounced valley between

the fenders, allowing at

least a modicum of rearward vision. This space was often filled by a supplementary wing, which both

reduced drag and increased rear downforce, but this advantage was to some extent offset by a reduction in front-end downforce. As illustrated, the standard 917K

had a Cd of 0.447, which was improved to 0.438 by fitting the extra wing.

45

22. Four resistors — one for each ignition circuit — are located within the engine bay.

23. Two distributors are provided, each serving one bank of cylinders, there being two plugs per cylinder. Each plug lead is numbered,

this being an essential

feature of many-cylindered engines; there have been

cases where teams with less forethought have lost valuable time attempting to sort out plug leads following work carried out at pit stops

24 & 25. Four separate ignition systems are used, each covering three cylinders, the ‘black boxes’ being fitted to

the rear bulkhead within the cockpit, along with the automatic voltage contro/ boxes. Note the sliding panel in the not-very-clear rear window.

26. The 917’s engine protrudes through the rear deck,

and is covered by a fibreglass moulding which prevents the intake trumpets from ingesting foreign bodies.

27. Doors are hinged so as to open forwards, but there

is no means of holding them open, and they can easily fall on the unwary.

The style of the upper doors, the

side windows and the central portion of the bodywork is very similar to that used on the latest 962s.

28. The fuel filler on David Piper's 917 010 is in the same position as on the original coupés, but is of a more modern self-closing type which cannot spring

open accidentally. The vents in the front fender reduce pressure build-up and hence lift, and probably are of some assistance in brake cooling.

These louvres were

not to be found on the first production cars, but have

since been added to many examples.

29. The headlights are enclosed in plexiglass fairings, so that the lights can be used without affecting the vehicle's aerodynamics. It is a pity that legislation often prevents this system from being used on sporting road cars, which usually have to make do with unsightly and inefficient pop-up units. 917s were generally equipped with units by SEV Marchal (as used here) or by Cibié.

29

46

of 30. The tail section is hinged from the cockpit roof, and

36 & 37. Two large diameter tubes take air from the

fastened shut by means of two GEZE clips.

NASA

ducts in the rear bodywork down to the gearbox.

Note the Giubo ‘doughnut’ coupling just visible on the driveshaft, and the two exhaust outlets which cope with

the output of all twelve cylinders, earlier versions of the 31. The fire extinguisher plunger and ignition cutouts

917 used separate side outlets for the front three

are located immediately behind the left-hand door.

cylinders on each bank.

thee

32 & 33.

A NASA

duct in the /eft-hand rear fender

includes a cutout giving access to the oil filler cap, whilst on 917 010 the right-hand duct has its efficiency greatly impaired by a fuel filler atop the supplementary

tank. The ducts are intended to direct air to the gearbox.

34. The door release button and finger recess could hardly be sleeker.

35. The chassis number plate is welded to one of the tube joints at the back of the car.

47

38. Fuel collector tank acts as a final reserve supply, sufficient petrol being held to enable the car to complete at /east one /ap on any circuit.

39. This supplementary fuel tank installed beneath right rear fender is for use in Can-Am style racing where fuel capacity is unlimited, and the saving of a single pit stop

can mean the difference between winning and losing. The filler is illustrated in photo 33.

40. Bilstein shock absorbers are installed within

tapered-wire titanium springs.

41. Air from the two small ducts in the front of the nose is split so as to provide cooling for both brakes (via the

larger tube) and the cockpit.

48

42. This view of a 917 is rare indeed, as possibly only 917 010 has a completely detachable front end, most 917s using a small lift-out panel to give access to the radiator and wiper motor.

The radiator is, of course, for

cooling engine oil, not water!

43. Hydraulic reservoirs share the space at the front with chassis tubes, cockpit ventilator ducting, wiper motor

and anti-roll bar.

44. Massive front discs are seen here without their calipers, which had been removed for modification at

the time the picture was taken. Later versions of the discs were perforated, which allowed the brakes to run

cooler, and enabled water to be dispersed more quickly. Porsche used exotic materials to quite some extent, the

cone attached to the disc usually being in titanium, although in some cars aluminium was used. Hubs also

were titanium, but the discs themselves were cast iron.

49

45, The Le Mans

Test Weekend was a splendid

institution, giving teams the opportunity to test their latest modifications in good time before the race proper. /n 1971 the sessions saw the arrival of 917 052, which

used a chassis frame built in magnesium.

This was the

car's sole public appearance, as it was later tested to destruction to ensure the durability of the chassis. Its tail featured the vertical fins and shallower fender line

which were to become standard wear for 917Ks in use on longer tracks.

Taping over the joints between body

panels reduced the risk of air getting under the panels and forcing them open, and also helped keep a smooth boundary /ayer.

46. The shape of the tail of the 917K owed much to this car, the first 917PA, 917 028, which was raced by

Siffert in the 1969 Can-Am series, the team being managed by Richie Ginther.

Whilst in the USA the car

suffered a great deal of modification, and ended up resembling a 917/10.

47. 917 053 was the ultimate works 917K, running only at Le Mans in 1971 and winning that race comfortably. /t used a magnesium chassis, which was so light that the car had to be ballasted by the inclusion of a special

12-gallon oil tank, to bring it up to the minimum weight of 800kg. Drivers were Helmut Marko and Gijs van Lennep, and they succeeded in covering a still unbroken

record distance in the white Martini-entered car. ae by oe

48, 49, & 50. Close scrutiny of photo 48 will reveal that the engine bay of the PA spyder 917 027 has no fewer than sixteen injection trumpets nestling within it. This is

condition seen here, to the Porsche Museum reserve

proof that the legendary 16-cylinder boxer motor was

collection. Note that the bodywork is basically standard

actually installed in a 917, although no car was ever

PA style, but with the addition of aluminium strips to

raced with that engine. Several capacities were tried,

the lower edge of the nose, and with a gearbox

ranging from 5 litres up to 7.2 litres. The smallest

oil-cooler attached to the tail.

version was eligible for Manufacturers’ Championship races, but as things turned out the 5-/itre flat-12 proved

51 & 52. The 16-cylinder motor is a most impressive

adequate to see off the opposition. Bore and stroke of

piece of machinery, and it is a great pity that it was

the small flat-16 were 80mm by 62mm, giving a total

by-passed after the arrival of turbocharging.

capacity of 4982cc and a power output of 690bhp at

example illustrated here has a bore of 90mm and a

The

9200 rpm. 917 027 was used as Porsche's development

stroke of 70.4mm, giving a capacity of 7166cc; its

hack, and was eventually relegated, in the well-used

power output was a tremendous 880bhp at 8300rpm.

53. There is little difference between the external dimensions of the 12-cylinder and the 16-cylinder engines, so there was no difficulty in fitting the 16 into the back of the 917.

Sea

we brenstrarcinw st

55

56

Truffeljager, le Cochon Rose and Big Bertha, the Pig

that, even with a drag co-efficient of only 0.387, its

at the 1971 Le Mans Test Weekend, and took part in

qualified seventh on the grid, with a time of 3m217.0s.

total drag was fractionally higher than that of the finned

the three-hour race which was held there. In its plain

Drivers Reinhold Jost and Willi Kauhsen got 917/20

version of the 917K. Nonetheless, its on-track

white paintwork the stubby car looked especially ugly,

007 up to 3rd place at one stage but Jost put it off the

performance suggested that the aerodynamics were

and it became the target of many a rude remark.

road at Arnage half way through the race. The car's

actually better than the wind-tunnel indicated.

Porsche rose to the occasion, and when the car

unusual shape was developed by the French concern

54, 55 & 56. The one and only 917/20 made its début

reappeared at the 24-hour race in June it had been

SERA, and was intended to combine the low drag of a

repainted in pig-pink, with the appropriate cuts of meat

langheck with the downforce ofa K. It did not quite

written boldly across it! Variously dubbed der

work out that way, as its great width (87 inches) meant

52

57 & 58. Mark Donohue drove the Penske-prepared

/&M-sponsored 917 10 005 and.917/10 011, both

917/10s in the 1972 Can-Am but an injury sustained in

being turbocharged and the /atter having

an accident during practice for the second round of the

frame. These photographs show Donohue

series meant that he was able to contest only the first,

Mosport, the first round, where he finished second after

seventh, eighth and ninth rounds. In those he scored

@ pit-stop to clear a sticking butterfly-valve in the

enough points to come third overall in the

turbocharger system.

Championship.

a magnesium testing 011 at

The cars he used were the

=

a

a ae

ee

59. After Donohue’s accident, George Follmer took over the driving chores for the Penske team, and used 917/10 003 to win the 1972 Can-Am Championship by a handsome margin, scoring 130 points, exactly double the score of second-place man Milt Minter in his unturbocharged 917/10 004. The picture shows Follmer

at Watkins Glen, where he finished fifth. The car used the shovel-nosed design which was adapted /ater for the 917/30, but this style was not used on all series 10 cars. Note that behind Follmer and the Lola (No.1) are

two further 917/10s, these being Minter’s (on the right)

and Pete Gregg’s; both used front bodywork similar to the 1971 917 langheck.

60. Roger Penske’s cars have always been looked upon as examples of the highest standards of preparation, and

his 917/30s were no exception.

The cockpits were clean

and neat, but were still businesslike, with no unnecessary frills. Instruments and controls were very

similar to those of the 917K, but were arranged slightly differently; the six buttons on the simple panel were,

from the left, ignition system right bank and left bank, then fuel pumps, upper for left, lower for right. The ignition key is no longer used, and the large rev counter is red-lined at 8000rpm.

61. The turbocharged engine of the 917/30 is the most powertul ever to have been used in circuit racing cars, and it was by no means at the limit of its development

when the programme was terminated after the 917/30

was legislated out of Can-Am. Note here the twin elongated inlet manifolds, the usual cooling fan, and the hefty roll-over bars.

54

62 62 & 63. Donohue’s first race finish in the Sunoco

car or in 917/30 002; truly the 917/30 was a formidable

and that its power output had gone from 580bhp to

Porsche was at Road Atlanta, in 917/30 003, seen here.

machine. It is interesting to note that between the

1100bhp!

He finished second in the blue and yellow Porsche, and

introduction of the first 917 in 1969 and the arrival of

won every subsequent Can-Am in 1973 either in this

the 917/30 in 1973 the car's shape had changed totally,

ee %.

55

ad coon

——o &

SEAR,

:

S(Martinipel >

64 64, 917/30 007 was built with an adjustable length chassis, for research into alternative whee/bases for /ater 917/30s.

When its experimental days were over, it was

reset at the standard wheelbase of 90.6inches and given a 917/10

tail before being passed on to the Martini

Racing Team for use in the Interserie. With Herbert Muller driving, the car secured the Championship in

1974, when turbocharged cars were restricted to 4.5-litres capacity.

56

John Allen has an abiding enthusiasm for sports car racing and, since 1968, has attended every Le Mans 24-hour race. His main interest, though, is in the technical details of racing cars rather than the actual racing, an understanding which has given him great respect for Porsche's remarkable attitude towards sports car racing. John is of the opinion that the 917, in particular, is one of the all-time great racing cars, especially after seeing them race in their heyday which he found tremendously exciting.

John has a variety of interests apart from sports car racing which he lists as aviation, amateur dramatics and photography, whilst also being able to play the guitar. He is a Manager with a firm of Chartered Accountants based in Leeds, were he has lived all his life. This is his second book for the Haynes Publishing Group, the first title being Ford G7T40 Super Profile.

ISBN O-85429-495-3

|

/P €$p-4JHO

9"780854"2949541