Tony Rudd began designing the BRM H16 engine in 1964, effectively combining two 1500cc V8s. It was a very complex engine and the project took a very long time to finish. The BRM P83 equipped with this 2998cc engine was a rather conventional single-seater, which was only ready for the 1966 Italian GP. For the rest of the season, the BRM team used the old P61 / 2s. Both Stewart and Graham Hill raced the last three GPs of the season with the P83, both retiring on all occasions.