Coventry Climax
Hayes next project came about as an approach from Colin Chapman. Chapman's cars had until that point relied on power from fast revving Coventry Climax engines, but with the change in Formula One regulations to three litre capacity from 1966, Coventry Climax decided for business reasons not to develop a large capacity engine. Chapman had approach the fledgling Cosworth group, with Keith Duckworth commenting that he could produce a competitive three litre engine, given a development budget of £100,000.