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The R-4360 was a 28-cylinder four-row air cooled radial engine. 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. 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.
Engine displacement was 4,362.50 cubic inches (71.5 L), hence the model designation. Initial models developed 3,000 hp (2,240 kW), but the final models delivered 4,300 hp (3200 kW) using two large turbochargers in addition to the supercharger. Engines weighed 3,482 to 3,870 lb (1,579 to 1,755 kg), giving a power to weight ratio of 1.11 hp/lb (1.83 kW/kg), which was matched by very few contemporary engines.
Wasp Majors were produced between 1944 and 1955; 18,697 were built.
A derivative engine, the R-2180-E Twin Wasp E, was essentially the R-4360 "cut in half". It had two rows of seven cylinders each, and was used on the postwar Saab 90 Scandia airliner.
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