Editing Sports car racing (section)

===1960s and 1970s &ndash; Evolution, rise, and decline===
[[Image:2006FOS 1970Porsche917KGulf.jpg|thumb|right|An iconic 1970 [[Porsche 917]] at the 2006 [[Goodwood Festival of Speed]]]]
Powerful prototypes (effectively pure-bred two-seater racing cars with no real link to production vehicles) started to appear as the 1960s progressed, with worldwide battles between Ferrari, Ford, Porsche, Lotus, Alfa Romeo and [[Matra]] as well as other more specialist marques running on into the early 1970s. The competition at Le Mans even made it to the movie screens, with [[Steve McQueen (actor)|Steve McQueen]]'s film [[Le Mans (film)|Le Mans]]. This era was seen by many as the highpoint of sports car racing, with the technology and performance of the cars comfortably in excess of what was seen in Formula 1. [[Homologation]] saw many out-and-out racing cars produced in sufficient quantities to see them classed as production vehicles; the FIA responded by placing more restrictions on even the allegedly production-based cars and placed draconian limits on the power available to prototypes&nbsp;– these prototypes of the late 1960s/early 1970s were comfortably quicker than contemporary Grand Prix machinery and for 1972 they were constrained to run much smaller engines to F1 rules, often de-tuned for endurance. [[Group 4 (racing)|Group 4 Grand Touring Cars]] and [[Group 5 (racing)|Group 5 Special Production Cars]] became the premier form of "sports car" racing from 1976, with prototypes going into a general decline apart from [[Porsche 936]] domination at Le Mans and a lower-key series of races for smaller two-litre [[Group 6 (racing)|Group 6]] prototypes.

A peculiarly American form of sports car racing was the [[Can-Am]] series, in which virtually unlimited sports prototypes competed in relatively short races. This series ran from 1966 to 1974 and was an expansion of the [[United States Road Racing Championship|USRRC]] that conformed to [[Fédération Internationale de l'Automobile|FIA]] Group 7 rules. The original [[Can-Am]] fell victim to rising costs and the [[1973 energy crisis|energy crisis]].

The ACO, organisers of the Le Mans 24 Hours, attempted to come up with a formula that would encourage more prototypes back to the race but would also be relatively economical&nbsp;– their Grand Touring Prototype rules in the late 1970s, based on fuel consumption rules, gave rise to two different varieties of sports car racing that were widely held to be a high point in the history of the sport.