The Pratt & Whitney R-985 “Wasp Junior” is a 9-cylinder, air-cooled radial aircraft engine widely used in the U.S. and abroad in the 1930s. Introduced to complement the Pratt & Whitney “Wasp” and “Hornet” families of engines, the U.S. Army Air Corps first used the smaller 300 hp “Wasp Junior” in 1932. Improving throughout WWII, the engine eventually produced 450 hp. The R-985 met the needs of a wide variety of military and commercial aircraft, including trainers, transports, aircraft, and helicopters.
Pratt & Whitney R-985 "Wasp Junior"

Model: R-985-AN-14B
Type: 9-cylinder air cooled radial
Displacement: 985 cu in
Maximum RPM: 2,300
Maximum horsepower: 450
Type: 9-cylinder air cooled radial
Displacement: 985 cu in
Maximum RPM: 2,300
Maximum horsepower: 450

Image Credit: Excerpt from Wasp Promotional Brochure, by Pratt & Whitney