ACL Porsche 917 K

Porsche first revealed the 917 to the press at the 1969 Geneva Motorshow. This was followed by an intense CSI homologation inspection, demanding that all the cars needed to be complete before the car could race. Remarkably, Porsche produced eight more cars in three weeks to complete the necessary 25 cars. On April 1st, 1969 the 917 was homologated just in time for Le Mans.

During initial tests, the 917 was found to be particularly unstable and many driver’s began to have doubts about its design. Brain Redman said 'it was incredibly unstable, using all the road at speed.' It was thought that the engine might be too powerful for the chassis and the much less powerful 908 was preferred by the factory drivers. At the 1000km of Spa, a long tail 908 was chosen in favor over the 917.

For the 1970 season, 917s were sold to Martini Racing, JWA Gulf Racing and Porsche Salzburg—all private teams that would be supported by the factory. Under the direction of John Wyer, the engineers at JWA tackled the handling problems first discovered in testing. Wyer’s engineer, John Horsmann, came up with a solution to hack off the rear section of the bodywork and replace it with a new aluminum section. This greatly improved stability by increasing downforce at the expense of drag. Porsche later made revised tail sections for most of the cars and called the cars Kurzheck or 917K.