Dr.-Ing. h.c. F. Porsche AG, usually shortened to Porsche AG, is an automobile manufacturer specializing in high-performance sports cars, SUVs and sedans.
A variant of the 917K appeared with a less upswept tail and vertical fins, and featured the concave rear deck that had proved so effective on the 1970 version of the 917L (see below). The fins kept the clean downforce inducing air on the top of the tail and allowed the angle of the deck to be reduced, reducing the drag in direct proportion. The result was a more attractive looking car that maintained down force for less drag and higher top speed.
The 917K models were generally used for the shorter road courses such as Sebring, Brands Hatch, Monza and Spa-Francorchamps. The big prize for Porsche however, was Le Mans. For the French circuit's long, high speed straights, the factory developed special long tail bodywork that was designed for minimum drag and thus highest maximum speed. On the car's debut in 1969, these long-tail (917L) models proved to be nearly uncontrollable as there was so little down force. In fact, they generated aerodynamic lift at the highest speeds.
The 917/20 #20 was chassis N°917/20.001 and it was driven by Kauhsen and Siffert. This particular car (#20) would be driven in the actual 24 hour race of 1971 at the hands of Kauhsen-Jöst.