Carroll moved to Europe where he befriended John Cooper. Driving a Formula Junior Cooper, he won his first race. After waning success in the Cooper cars, followed by a characteristically clear-eyed personal assessment that he lacked the ability to drive race cars at the highest levels, he returned to the United States and began working with Carroll Shelby and the Ford Motor Company on the GT40 Le Mans program. Smith oversaw the preparation on the cars that won the 1966 and 1967 24 Hours of Le Mans.