The Swedish trio had begun work several years earlier, by combining the bottom end of a Volvo car engine with VW Beetle cylinders and a purpose-built cylinder head. When this proved promising, they began work to design and build their own powerplant, along very similar lines, using local experts for specialized tasks such as crankcase casting. The end product is an air-cooled, two-valve-per-cylinder engine whose 1845cc capacity comes from cylinder dimensions of 85.8 x 80.0mm. The heavily finned cylinder barrel and head sit above a crankcase whose shaft-drive combines BMW parts with revised ratios for the four-speed gearbox. Many parts are purpose-built. Others, including camshaft, crank, pistons and conrods, come from Volvo; valves are from VW.