It was the Ford Escort that really put Ford on the rallying map, proving capable of winning World Championship events from 1968, when the Twin Cam model was the works frontline rallycar, right through to 1981 when Ari Vatanen became World Rally Champion driving an Escort RS. In 1970 the Ford Twin Cam engine was replaced by a Cosworth BDA 16-valve unit to create the definitive Escort rally car, the RS1600, though the engine was, in fact, homologated at 1,601cc to enable future enlargement up to the 2-litre class capacity limit. The first full 2-litre engines were homologated in 1972 and in works trim produced 235-240bhp. In this ultimate form the Escort RS1600 proved good enough to win the RAC Rally three times on the trot between 1972 and 1974, as well as a host of other World Championship events.