Franklin O-150

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Franklin 4 AC-150-A (1938) aircraft engine - San Diego Air & Space Museum annex Gillespie Field.jpg
4AC-150 engine on display at the San Diego Air & Space Museum
Type Piston aircraft engine
National origin United States
Manufacturer Franklin Engine Company
First run 1938

The Franklin O-150 (company designation 4AC-150) was an American air-cooled aircraft engine of the late 1930s. The engine was of four-cylinder, horizontally-opposed layout and displaced 150 cu in (2 L). The power output was nominally 40 hp (30 kW).


Specifications (4AC-150)[edit]

Data from Jane's all the World's Aircraft 1938.[1]

General characteristics

  • Type: 4-cylinder air-cooled horizontally opposed aircraft piston engine
  • Bore: 3.625 in (92.1 mm)
  • Stroke: 3.625 in (92.1 mm)
  • Displacement: 149.6 cu in (2.45 l)
  • Length: 27.5 in (70 cm)
  • Width: 34.375 in (87.3 cm)
  • Height: 18.375 in (46.7 cm)
  • Dry weight: 155 lb (70 kg)


  • Valvetrain: Pushrod and rocker operated overhead valves. One intake, one exhaust
  • Fuel system: Stromberg NA-S2 updraught carburetor
  • Fuel type: 70 Octane gasoline
  • Oil system: Wet sump full pressure system
  • Cooling system: Air-cooled


See also[edit]

Comparable engines

Related lists


  1. ^ Grey, C.G.; Bridgman, Leonard, eds. (1938). Jane's all the World's Aircraft 1938. London: Sampson Low, Marston & company, ltd. p. 85d.
  • Gunston, Bill. (1986) World Encyclopedia of Aero Engines. Patrick Stephens: Wellingborough. p. 57