Porsche 917

Lore & Background

In an effort to reduce speeds at Le Mans, the CSI announced that the International Championship of Makes would run for three-litre Group 6 prototypes from 1968 through 1971, but also allowed five-litre Group 4 sports cars with a minimum of 50 units manufactured. In April 1968, the minimum production figure was reduced from 50 to 25, starting in 1969. Starting in July 1968, Porsche decided to conceive, design and build 25 versions of a new car with a 4.5-litre engine to win its first overall victory at Le Mans on June 14, 1970. In only ten months the Porsche 917 was developed, based on the Porsche 908. On March 12, 1969, a 917 was displayed at the Geneva Motor Show. On April 20, Ferdinand Piëch displayed 25 917s to CSI inspectors, offering to drive any of them, which was declined.

In Their Own Story

The Mulsanne Straight stretched into darkness at midnight. Richard Attwood gripped the wheel as the air-cooled flat-12 screamed past 6000 RPM. The nose lifted slightly under acceleration, a familiar dance with physics he had mastered over months of testing. Headlights cut through the dust and rain, illuminating the tarmac ahead. There was no room for error; one slip at this velocity meant disaster. He held his nerve, braking late into Mulsanne Corner, feeling the heat radiate from the discs as the crowd roared in the distance.

Reader's Guide

The car's chassis was designed by Helmuth Bott and the engine by Hans Mezger, under Ferdinand Piëch. The chassis was a very light spaceframe (42 kg) pressurised with gas to detect cracks. The 4.5-litre air-cooled flat-12 engine (Type 912) featured twin overhead camshafts, twin spark plugs, and a large horizontally mounted cooling fan. The driving position was so far forward that the driver's feet were beyond the front wheel axle. The original version had a removable long tail/medium tail with active rear wing flaps, banned in May 1969 after Formula 1 crashes. Handling problems were investigated in late 1969 at a joint test at the Österreichring, leading to the wedge-tail 917K (Kurzheck). In 1971, a variant of the 917K appeared with vertical fins and a concave rear deck. The engine was enlarged from 4.5 litres (520 bhp) through 4.9 litres (600 bhp) to 5 litres (630 bhp). The 917K models were used for shorter road courses; for Le Mans, the factory developed special long tail bodywork (917L) for minimum drag. In 1969 Jo Siffert raced an open-top 917PA Spyder in CanAm. Other variants include the 'Pink Pig' (917/20), and turbocharged 917/10 and 917/30 CanAm Spyders. In the 1973 Can-Am series, the turbocharged 917/30 developed 1,100 bhp.

Did You Know?

• The 917 gave Porsche its first overall win at the 24 Hours of Le Mans in 1970, driven by Hans Herrmann and Richard Attwood.
• The 917 repeated its Le Mans win in 1971.
• The Interserie championship began in 1970, and while 917 drivers won titles in 1970, 1971, 1972, and 1973, they did not win in 1974 or 1975.
• The original 4.5-litre engine produced around 520 bhp in 1969, later enlarged to 5 litres producing 630 bhp.