instead decided to focus on the North American markets and the Can-Am Challenge. For that series, larger and more powerful engines were needed. Although a 16-cylinder engine with about was tested, a turbocharged 12-cylinder engine with comparable power output was ultimately used. The 917 chassis also had to be lengthened to accept the longer 16-cylinder engine, and drivers complained that this longer chassis did not handle as well. The turbocharged 917/10K entered by Penske Racing won the 1972 series with George Follmer, after a testing accident sidelined primary driver Mark Donohue. This broke the five-year stranglehold McLaren had on the series. The further evolution of the 917, the 917/30 with revised aerodynamics, a longer wheelbase and an even stronger 5.4 litre engine with around in race trim, won the 1973 edition winning all races but two. Charlie Kemp won the Mosport race, George Follmer won Road Atlanta and Mark Donohue won the rest. Most of the opposition was made of private 917/10K as McLaren, unable to compete against the 917 turbos, had already left the series to concentrate on Formula 1 and the Indy 500. The 917's domination, the oil crisis, and fiery tragedies like Roger Williamson's in Zandvoort pushed the SCCA to introduce a 3 miles per U.S. gallon maximum fuel consumption rule for 1974. Due to this change, the Penske 917/30 competed in only one race in 1974, and some customers retrofitted their 917/10K with naturally aspirated engines. The 917/30 was the most powerful sports car racer ever built and raced. The 5.374-litre 12 cylinder (90.0 x 70.4 mm) twin-turbocharged engine could produce around at 7,800 rpm in race trim. The 917/30 dominated the Can-Am series during the 1973 season. The 917 was also the only championship winning car in Can Am not to be powered by Chevrolet. 1981 In 1981, it appeared that new Le Mans regulations would allow a 917 to race again. The Kremer Racing team entered a home-built updated 917, the 917 K-81. The car raced at Le Mans qualifying in the top 10 but retired after seven hours after a collision with a back marker led to a loss of oil and withdrawal. The final chapter though was to be at Brands Hatch where the car ran in the 6 hours at the end of the season. The car was competitive and ran at or near the front, including a spell in the