This V-1650 liquid-cooled engine was the U.S. version of the British Rolls-Royce Merlin engine. In 1942, the Packard Co. started building the Merlin engine for both the US and British, and adapted it for American mass-production methods. 55,873 Merlins were produced in the US for the P-51, Spitfires, Mosquitos, and Lancasters.