Allison V-3420-23 (V-3420-B10), Double V Engine

Type: Reciprocating, 24 cylinders, liquid-cooled,

Power rating: 1,939 kW (2,600 hp) at 3,000 rpm

Displacement: 56 L (3,420 cu in.)

Bore and Stroke: 140 mm (5.5 in.) x 140 mm (5.5 in.)

Weight: 1,485.5 kg (3,275 lb)

Originally known for modified Liberty engines, the V-1710 was the first truly Allison engine, and became the first American engine to qualify at 746 kW (1,000 horsepower) for the 150-hour military type test. It was the only liquid cooled engine that saw service in World War II, powering most war time U.S. Army fighters, including the P-38, P-39, P-40, P-63, and early P-51s.

In 1937, Allison began development of the V-3420, comprised of two V-1710 engines geared together on a common crankcase. This project resulted from an Army Air Corps interest in a 1,500 kW (2,000 hp) bomber engine. However, development was not pressed until late in the war because of the need for improving the V-1710. Plans were made for producing the V-3420 in large quantity for a high-speed, low-altitude fighter, the Fisher P-75, but only about 100 engines were produced before the project was dropped.

This engine powered the Fisher XP-75A and P-75A.