Conceived by Jules de Their and Henri Langlois Van Ophem, it debuted in 1924 over a 15 kilometres (9.3 mi) circuit on public roads between the towns of Francorchamps, Malmedy and Stavelot, under the auspices of the Royal Automobile Club Belgium (RACB). The present 7.004 kilometres (4.352 mi) circuit was inaugurated in 1979. The Spa 24 Hours was part of the European Touring Car Championship from 1966 to 1973, 1976 and 1982 to 1988 (except 1987 when it was part of the World Touring Car Championship). The event also counted towards the World Sportscar Championship in 1953 and the World Endurance Championship in 1981. As on the Nürburgring, both a 24h and a 1000 km (6Hr) race is held. Cars entered have spanned from the Russian Moskvitch and models with sub-1 liter engines such as the NSU Prinz TT to the luxurious V8-powered Mercedes-Benz 300 SEL 6.3. Tuned by Mercedes-AMG, the 6834 cc and 420 hp (313 kW) so-called "Red pig" finished as high as second in 1971.