There are at least eleven variants of the 917. The original version had a removable long tail/medium tail with active rear wing flaps, but had considerable handling problems at high speed because of significant rear lift.
The Porsche 917 is a race car that gave Porsche its first overall wins at the 24 Hours of Le Mans in 1970 and 1971. Powered by the Type 912 flat-12 engine of 4.5, 4.9, or 5 litres, the 917/30 Can Am variant was capable of a 0-62 mph (100 km/h) time of 2.3 seconds, 0–124 mph (200 km/h) in 5.3 seconds, and a top speed of up to 240 mph (390 km/h).
The handling problems were investigated at a joint test at the Österreichring by the factory engineers and their new race team partners John Wyer Engineering and after exhaustive experimentation by both groups, a shorter, more upswept tail was found to give the car more aerodynamic stability at speed.
Porsche 917K in the distinctive Gulf Oil livery.