Guide: Porsche 917 / 70 L
Background
Although the Kurzheck configuration had transformed the Porsche 917 from an unstable and ill-handling pig, the trade off was a big drop in top speed; these short tailed variants topped out at around 190mph whereas the long tailed cars from 1969 had exceeded 220mph.
At most circuits on the World Sportscar Championship calendar, this was not a problem and the 917 K’s improved dynamics led to much quicker lap times. However, with its exceedingly long straights, Le Mans was the exception.
To give themselves the best chance of victory at la Sarthe, Porsche developed a new Langheck version of the 1970 car.
Ferrari were also developing a long tailed version of their 512 S for Le Mans, but whereas the Italian firm simply opted for a bolt-on rear clamshell that could be fitted to any 512 S, Porsche went to the trouble of designing an entirely new low drag body for their car.
Bodywork
The 917 L was 52mm wider and 540mm longer than the 917 K.
It also had more pronounced surface curvature with bodywork that sunk away from the tops of the wings.
Re-shaped headlight cowls were introduced along with more rounded front corners.
The forward section of the cockpit was unchanged but behind it, the engine was enclosed rather than open to the elements.
The extended rear end flowed smoothly down towards the tail where two large cooling scoops were located.
The 917 K’s cutaway back end was replaced by a more conventionally shrouded tail complete with two huge vertical fins.
Chassis
Aside from its new bodywork, under the skin, the 917 L was little changed.
It employed the same lightweight tubular alloy spaceframe that was permanently gas-pressurised to detect any cracks in the structure.
Double wishbone suspension incorporated titanium coil springs with adjustable Bilstein dampers and magnesium uprights.
The ventilated disc brakes and calipers were supplied by Girrling.
15-inch diameter centre-lock magnesium alloy wheels were mounted on titanium hubs. Like the 917 K, the wheels measured 10.5-inches wide at the front and 15-inches wide at the back.
For 1970, Goodyear tyres would be used.
Engine & Gearbox
Although Porsche had their enlarged 4.9-litre version of the Hans Mezger-designed air-cooled 180° Flat 12 on stream soon after the 917 L made its debut at the Le Mans test weekend in April, both long tailed examples that attended the 24 Hour race used the standard 4.5-litre Type 912/00 engine.
This was the uprated 1970 version with its strengthened crankcase and twin pipe exhaust system.
It employed mechanical Bosch fuel-injection with two separate ignition distributors to feed the 24 spark plugs.
Compression was 10.5:1 and peak output was 560bhp at 8000rpm.
Given the enormous top speeds predicted, a five-speed gearbox was essential for Le Mans – a four-speed would have been bouncing off the rev limiter.
Testing
On April 6th, the first 917 L (chassis 040) was taken to Volkswagen’s high speed Ehra-Lessien test track where Kurt Ahrens Jr. conducted a shakedown one week before the annual Le Mans trials.
The test took place on a soaking wet day and Ahrens Jr. had an enormous accident coming off the banked section.
Chassis 040 aquaplaned into the barriers at around 160mph and split in two. The back half of the car travelled several hundred metres down the track.
Miraculously, Ahrens Jr. wasn’t seriously hurt but internal bruising prevented him racing for the next few weeks.
Frenzied work by the Porsche mechanics produced another 917 L in time for the Le Mans test (chassis 041).
1970 Le Mans Test
The date of 1970’s Le Mans test clashed with round three of the World Sportscar Championship at Brands Hatch so it was rather poorly attended and wet weather kept lap times down.
Herbert Linge was on hand to drive the new plain white long tailed car which appeared only briefly and posted 15th quickest time.
Also present was the Gulf Oil-backed John Wyer Automotive Engineering team (JWAE) who went fastest with their 917 K in the hands of Brian Redman and Mike Hailwood.
Subsequent Tests
Further testing was carried out over the next few weeks during which time, chassis 041 was destroyed in another high speed crash.
This and the earlier incident convinced John Wyer not to run the 917 L at Le Mans. His team ran a trio of 917 Ks instead.
1970 Le Mans 24 Hours
Despite its reputation for instability in fast corners and a liability to aquaplane in the wet, Porsche entered two new 917 Ls for Le Mans.
One was for the quasi-works Salzburg team (042) and the other was entered under the Martini Racing banner and run by Porsche themselves (043).
Each car had a full width rear wing added between the tail fins to improve stability.
The Salzburg entry was painted white with red airflow stripes. It was allocated to Vic Elford and Kurt Ahrens Jr. who qualified on pole with a time just two tenths of a second quicker than the works Ferrari 512 S of Nino Vaccarella and Ignazio Giunti.
Jo Siffert and Brian Redman started third in their JWAE 917 K followed by another 512 S (Merzario / Regazzoni) and the sister JWAE car of Rodriguez / Kinnunen in fifth.
The Martini-backed 917 L of Gerard Larrousse and Porsche test driver, Willi Kauhsen, qualified twelfth. This car arrived at Le Mans in a wild purple livery with white psychedelic stripes to which green centres were added after qualifying.
Backing up these cars were a further three 917 Ks including another from JWAE, one from Salzburg and one from the AAW Racing Team.
The race was held over June 13th and 14th and Porsche were determined to break their duck. Crushingly, the JWAE Ford GT40s had beaten them by a tiny margin in 1968 and again in 1969.
A high attrition rate with heavy rain overnight saw only 16 of the 51 starters go the distance. Two 917 Ks retired with crash damage, one blew its engine and another threw a con rod.
By early Sunday morning, just three 917s remained at which point the white and red Salzburg Langheck of Elford / Ahrens Jr. held a convincing lead.
However, handling problems caused by an unidentified slow puncture began to plague the car. It had dropped to second by 8:30 on Sunday morning when it came in with a broken inlet valve and was retired.
By this time, the purple and green Martini-backed 917 L of Larrousse / Kauhsen was struggling; the wet weather had affected its electricals but both this and the remaining 917 made it to the finish.
Despite having been the slowest 917 in qualifying, Porsche Salzburg’s 4.5-litre orange and white Kurzheck driven by Richard Attwood and Hans Herrmann took the win. Five laps behind in second place was the purple and green Martini Langheck driven by Larrousse / Kauhsen.
Porsche had recorded their maiden Le Mans victory and a revamped 917 L would be back again for 1971.
Text copyright: Supercar Nostalgia
Photo copyright: Porsche - https://www.porsche.com
