Read: H-D Shovelhead Engine

The Shovelhead was an air-cooled, 45 degree, V-twin motorcycle engine manufactured from 1966 to 1984 by the Harley Davidson Motor Company. It had 1,200 cc (73 cu in) of displacement and, after 1978, was increased to 1,340 cc (82 cu in) for Harley's Big Twin bikes. The "shovel" cylinder head represented an offshoot of the panhead design it replaced in 1966[1] 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. 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.

Fonte: Wikipedia