Pratt & Whitney R-4360 Wasp Major radial engines,
4 of the 8 engines on the Hughes H-4 Hercules (Spruce Goose)
The R-4360 was a 28-cylinder four-row air cooled radial engine 4,000 hp (2,640 kW). Each row of pistons was slightly offset from the previous, forming a semi-helical arrangement to facilitate efficient airflow cooling of the successive rows of cylinders, with the spiraled cylinder setup inspiring the engine's "corncob" nickname. A mechanical supercharger geared at 6.374:1 ratio to engine speed provided forced induction, while the propeller was geared at 0.375:1 so that the tips did not reach inefficient supersonic speeds.
Although reliable in flight, the Wasp Major was maintenance-intensive. Improper starting technique could foul all 56 spark plugs, which would require hours to clean or replace. As with most piston aircraft engines of the era, the time between overhauls of the Wasp Major was about 600 hours when used in commercial service.
The plane is on display at the Evergreen Aviation Museum, McMinville, Oregon