The FIA decreed from 1966, new 3-litre engine regulations would come into force. Lotus were less competitive. Starting with a 2-litre Coventry-Climax engine in the Lotus 33, Clark did not score points until the British Grand Prix and a third place at the following Dutch Grand Prix. From the Italian Grand Prix onwards Lotus used the highly complex BRM H16 engine in the Lotus 43 car, with which Clark won the U.S. Grand Prix. He also picked up another second place at the Indianapolis 500, this time behind Graham Hill.