The Mikulin AM-37 was a Soviet aircraft piston engine designed prior to Russia's entry into World War II.
An improved version of the Mikulin AM-35 V-12 engine, it was only produced in small numbers because of its unreliability.
24 in Moscow built only twenty-nine AM-37s, as the new engine was designated, in 1941 before the German advance forced the factory to evacuate in October.
Mikulin had been unable to resolve the issues with the AM-37 in the meantime and production was not resumed.
[1] Data from Kotelnikov, Russian Piston Aero Engines Related development