|Porsche 917 PA Spyder|
With a little encouragement from Vasek Polak, the Porsche and Audi distributor for California, Porsche decided to build a Group 7 version of the recently introduced 917 Group 5 sports racer to compete in the 1969 Canadian-American Challenge Cup (Can-Am for short). First established in 1966, the Can-Am Cup had quickly become one of the most popular and lucrative series in North America. At the time of Porsche's arrival, Can-Am was dominated by the seemingly unsophisticated big-block Chevrolet engined McLarens.
The Group 5 World Championship ended early in August and by that time Can-Am had already begone. Considering the limited time available, it was no surprise that the Porsche engineers only performed the absolutely necessary changes on the existing design to turn the 917 Coupe into a Can-Am car. The new 917 PA (for Porsche Audi) featured a roadster body, a larger fuel-tank and wider rear wheels. The weight was cut by 55 kg thanks to the removal of the roof and the heavy windscreen.
What remained was the pressurized aluminium spaceframe chassis and the fully independent suspension. Also left unchanged was the beautiful quad-cam flat 12 engine that displaced just under 4.5 liter and produced a hefty 580 bhp. Just like on the fixed-head 917s the exhaust exited ahead of the rear wheels. The new roadster body was very similar in shape to the three-liter 908 Spyders that were raced alongside the 917 in the World Championship that season. Fully equipped, the Porsche 917 PA tipped the scales at 775 kg.
Two examples were constructed; one was sent to North American while the other was retained by Porsche for testing purposes. Less than a week after winning the last round of the championship at Zeltweg in the regular 917, Swiss racer Jo Siffert first took to the track in the 917 PA. The white Porsche sported two blue stripes with 'Porsche Audi' markings and the starting number 0. The machine's debut came at the Mid-Ohio race, which was the first round of the championship. Five seconds off the pace, Siffert still managed to finish in a highly commendable fourth place.
A quick glance at the spec sheet explained why the new Porsche was no match for the still dominant McLarens. Their all-alloy Chevrolet V8 engines had a lot more torque and were also considerably lighter than the complicated Porsche V12. The McLaren aluminium monocoque also weighed considerably less than the Porsche. The total difference between the two was a startling 140 kg. The one thing the Porsche had going for itself was rock-solid reliability provided by its endurance racing roots.
Siffert was not deterred by the performance gap and continued to race the car with verve and consistency in the remaining races. He finished on the podium once and despite missing the first four races, ended the year in a highly impressive fourth in the championship. During the year various changes were carried through. The only mechanical modification concerned the exhaust pipes, which were routed out the back. Porsche's engineers paid specific attention to the aerodynamics and before the season was over the car sported a sharp 'shovel' style nose.
Porsche turned all of their attention to the world championship and the all-important Le Mans round during 1970 and 1971, so the 917 PA received no further updates. Siffert's old car was sold to Vasek Polak, who entered the car for several more seasons for his own driver Milt Milner. In 1972 and 1973 the car even featured the turbocharged engine that Porsche had developed for their new 917/10 Can-Am car. Three more cars were built along the lines of the 917 PA for the European Interseries championship. Porsche's own car was used for testing and currently sports an experimental 16-cylinder engine.
With a single podium finish, the Porsche 917 PA was certainly not the most successful Can-Am car built. Having won Le Mans twice, Porsche gave it another go and developed the bespoke 917/10. This initially featured a naturally aspirated engine but was soon equipped with a twin-turbo version of the flat-12. Porsche drivers were crowned champions in 1972 and 1973. The lessons learned with the 917 PA were fundamental for the later successes. Even if the 1969 season did not yield victories, just being there must have also achieved the exposure sought by Vasek Polak in the first place.
Article by Wouter Melissen, last updated on August 06, 2009
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