Harley-Davidson Shovelhead engine
The Shovelhead is an air-cooled, 45 degree, V-twin motorcycle engine manufactured from 1966 to 1984 by Harley-Davidson. Initial models had an engine displacement of 1,208 cc (74 cu in). During production of the 1978 model year, this was increased to 1,340 cc (82 cu in) for Harley's Big Twin bikes.[1] 1978 model shovelheads with the larger engine displacement are sometimes called 1978½ models.
The "shovel" cylinder head represented an offshoot of the panhead design it replaced in 1966[2] but featured a slightly different look. The name was derived from the appearance of the rocker box covers. Because these covers bring to mind the head of coal shovels when inverted, the name shovelhead was a natural progression. The shovel engines powered Harleys up until the introduction of the Evolution engine in 1984, ending the reign of the "shovel" as enthusiasts frequently call these engines. The shovel engine does not have covers, per se, but rocker boxes and rocker arms which pivot on shafts. The design provided more than a unique look; it produced 10% more horsepower than the panhead engine which it replaced. From 1966 through 1969 the shovelhead kept the panhead style lower end. These early style shovelheads with the generator bottoms were often referred to as slabside shovels. From 1970 on the shovelheads used an alternator bottom often termed a cone shovel.
A number of third-party engine manufacturers produce custom Shovelhead-style engines, in a variety of bores, many much larger than the original design displacements. Each manufacturer includes upgrades to the original design to improve the performance and reliability while still providing the original styling and overall engine structure.