Formula One regulations
Colin Chapman's Lotus 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 approached the fledgling Cosworth group, with Keith Duckworth commenting that he could produce a competitive three litre engine, given a development budget of £100,000.