Harley-Davidson Knucklehead engine

Common card · No. 371273

The knucklehead is a retronym used by enthusiasts to refer to the first Harley-Davidson motorcycle engine with overhead valves (OHV), introduced in 1936, and so named decades later because of the distinct shape of the rocker boxes and newer models showing different shapes. The Knucklehead engines and models were originally referred to as "OHVs" by enthusiasts of the time and in Harley's official literature. The new type was introduced in 1936 with 61 cui (1000cc) as Model E, ES with sidecar, or EL for higher octane leaded gasoline and impressive 40 hp. In 1941, the larger capacity 74 cui (1200cc) versions were called F and FL (48 hp), with Harley-Davidson FL designating many Harley big twin models ever since. Since 1929, Harley had offered Flathead engines in two sizes, with the VL model being the top-of-the-line model, but still featuring Total-loss oiling system and the simple and reliable but inefficient side-valve engine with the combustion chamber next to the piston, over the standing...

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