What is the largest piston aircraft engine?
The Lycoming XR-7755 holds the title of the largest piston aircraft engine ever built in the United States. With a massive 36-cylinder design, it boasted a displacement of about 7,750 cubic inches and produced 5,000 horsepower. The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial piston aircraft engine designed and built during World War 2. First run in 1944, it is the largest-displacement aviation piston engine to be mass-produced in the United States, and at 4,300 hp, the most powerful.