The Yakovlev M-501 was even bigger than the Lycoming XR-7755. A water-cooled, diesel, four-stroke, aircraft engine with 42 cylinders and 8760 cubic inches. It produced 4760 HP without and 6205 HP with turbocharger. It was intended for long-range strategic bombers, but its development was cancelled in 1953, in favour of the upcoming jet engines. Its basic configuration was used for the marine-engine Zvezda M503.
Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines | Old Machine Press