AMC AV-108-4 air-cooled V4 engine

The AMC AV-108-4 is an air-cooled V4 engine designed by American Motors Corporation, with a displacement of 108 cubic inches, about 1.8 litres. It was built for a single purpose, to power the M422 Mighty Mite, a lightweight aluminium-bodied military vehicle made from January 1960 to January 1963 so that the helicopters of the time could carry it for the United States Marine Corps. Its small size and modest output of 52 horsepower, about 39 kilowatts at 3,600 rpm, with 90 pound-feet of torque at 2,500 rpm, suited that job but made it unsuitable for ordinary passenger cars. Bore and stroke were both 3.25 inches and the compression ratio was 7.5 to 1. Unlike the fours AMC later bought in from outside suppliers, this one was designed in house, and it was never used in a regular AMC car.