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


Display Status:

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.

Collection Item Summary:

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.

Collection Item Long Description:


Circa World War II

Inventory Number


Physical Description

  • 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)

Credit Line

Transferred From USAAF

Country of Origin

United States of America


Aluminum, Steel, Magnesium, Paint, Copper, Rubber, Wood, Phenolic, Preservative coating


Height 104 cm (40.9 in.), Width 152.2 cm (59.9 in.), Depth 685.8 cm (270 in.)

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum


PROPULSION-Reciprocating & Rotary