The Jacobs R-755 (company designation L-4) is a seven-cylinder, air-cooled, radial engine manufactured in the United States by the Jacobs Aircraft Engine Company.  It was first produced in 1933 and was still in production in the 1970’s. It was used to power a variety of aircraft, including the Beechcraft Model 17 Staggerwing, the Boeing-Stearman PT-18 and various WACO aircraft.

Specifications

• Type: 7-cylinder air-cooled radial piston engine
• Power Output: 245HP @2200 RPM
• Bore: 5.25 in (133 mm)
• Stroke: 5 in (130 mm)
• Displacement: 757 cu in (12.4 L)
• Length: 37 in (940 mm) overall
• Diameter: 43.5 in (1,100 mm)
• Dry weight: 505 lb (229 kg)

Components

• Valvetrain: 2 valves per cylinder, pushrod-actuated, sodium-cooled exhaust valves
• Fuel system: Single Stromberg NA-R7A carburetor
• Fuel type: 73 octane
• Oil system: One pressure pump, two scavenge pumps
• Cooling system: Air-cooled
• Reduction gear: Direct drive, right hand tractor