Formula A (SCCA)

Formula 5000 (or F5000) was an open wheel, single seater auto-racing formula that ran in different series in various regions around the world from 1968 to 1982. It was originally intended as a low-cost series aimed at open-wheel racing cars that no longer fit into any particular formula. The '5000' denomination comes from the maximum 5.0 litre engine capacity allowed in the cars, although many cars ran with smaller engines. Manufacturers included McLaren, Eagle, March, Lola, Lotus, Elfin, Matich and Chevron.

In its declining years in North America Formula 5000 was modified into a closed wheel, but still single-seat sports car racing category.

Formula 5000 was introduced in 1968 as a class within SCCA Formula A races, a series where single seaters from different origins were allowed to compete, but which rapidly came to be dominated by the cars equipped with production-based American V8s. The engines used were generally 5 litre, fuel injected Chevrolet engines with about 500 horsepower (370 kW) at 8000 rpm, although other makes were also used. The concept was inspired by the success of the Can-Am Series, which featured unlimited formula sports cars fitted with very powerful engines derived from American V8s; the idea was to replicate the concept using open wheel racing cars. F5000 enjoyed popularity in the early 1970s in the U.S. and featured drivers such as Mario Andretti, Al Unser, Bobby Unser, James Hunt, Jody Scheckter, Brian Redman, David Hobbs, Tony Adamowicz, Sam Posey, Ian Ashley, John Cannon and Eppie Wietzes.

...
Wikipedia