aluminum 7-liter Chevrolet 'big block' engine replaced the 5.3-liter engine of the 2D. While always extremely fast, the extra power of the larger engine was too much for the automatic transmission to handle and it broke with regularity. After solving the transmission problems, the 2F scored its only win on 30 July 1967 in the BOAC 500 at Brands Hatch with Hill and Mike Spence driving. After this race the FIA changed its rules, outlawing not only the 2F but also the Ford GT40 Mk.IV (winner at Le Mans that year) and the Ferrari 330 P3/4 (winner, 24 Hours of Daytona) and 365 P4 (finished second, Le Mans). As with the 2D, the 2F raced wearing Texas license plates. The 1967 2G was a development of the 2E. It featured wider tires and a 427 cu in aluminum Chevrolet V-8 engine. While on par with its competitors in terms of power, the lightweight 2C chassis was stretched to the limit and it was only Hall's driving skills that kept the car competitive. For the 1968 Can-Am series, still larger tires were added to increase grip. Hall's racing career was effectively ended in a severe crash at the Stardust Grand Prix Can-Am race when he rear-ended the slow-moving McLaren of Lothar Motschenbacher, although he did drive in the 1970 Trans-American Sedan Championship while fielding a team of Chevrolet Camaros. Hall noted that the increasing downforce also created enormous drag. Seeking a competitive edge, the highly advanced 2H was built in 1968 as the replacement for the 2G to minimize drag. Not only was it extremely slippery it was narrow to reduce frontal area. Development problems kept it out of the Can Am series, forcing Hall to update the 2G for the 1968 series, during which his catastrophic accident occurred. Hall was consistently the best driver for Chaparral and knew how to get the best out of his cars. John Surtees was brought in as driver for the 1969 Can Am series but never figured out how to drive the 2H to take advantage of its low drag potential. Surtees complained he couldn't see out of the car and demanded a redesign which ruined the aerodynamics, then ran the rear wing almost upright, negating any advantage of the compact slippery shape. Ultimately, by 1969 the massive amount of power being generated from the big block Chevrolet engines that Hall effectively debugged in