The M-71 radial engine was developed from the Shvetsov M-70, a failed attempt at a two-row version of the single-row Wright R-1820 Cyclone. It used components from the Shvetsov M-63, which was an improved version of the M-25 with more horsepower than the original. Development began at the beginning of 1939 and it was bench tested that August, but did not pass its State acceptance tests until the autumn of 1942. It weighed 970 kg (2,100 lb) and produced 2,000 hp (1,500 kW). Despite this it was flight-tested in a Polikarpov I-185 prototype fighter in March–April 1942. A boosted version, the M-71F, was built in small numbers. It was flown in the prototypes of the single-engined Su-6 and the twin-engined Su-8 ground-attack aircraft in 1943–44 as well as the La-7 fighter in 1944. A version of the M-71F was developed with two TK-3 turbochargers and flight tested in the DVB-102 high-altitude bomber designed by Vladimir Myasishchev during the summer of 1943. Evaluations of the M-71 were generally favorable, but no production capacity was available to use for a brand-new engine during the war.