Both were supercharged, inverted V, air-cooled engines.
[2] The HM 512 shared the same bore and stroke (105 mm × 115 mm) and 6:1 compression ratio with the rest of the HM500 series air-cooled engines.
Other shared features were Hirth's use of roller bearings in the crankshaft and at both ends of connecting rods.
The crankshaft was of typical Hirth multipart design, the 12-cylinders requiring 7 roller bearings.
Handbuch der deutschen Luftfahrt- und Zubehör-Industrie 1944,[4] Jane's all the World's Aircraft 1938[3]