Contrary to popular belief, the brand's iconic, influential and enduring V-twin engine initially landed with a resounding ...

In fact, the manufacturer had an entire line of head-themed engines, including the Knucklehead, Panhead, and Shovelhead, with some featuring in the rarest Harley-Davidson motorcycles ever built.

Curious about Top Fuel Harley horsepower? Discover how much power these beasts pack and how fast they can really go.

The Harley-Davidson EL motorcycle was nicknamed the Knucklehead ... another entry into its "head" series of engines, the Shovelhead, given its name because of its shovel-shaped rocker covers.

Harley-Davidson's Twin Cam 103 and Milwaukee Eight 107 engines have their similarities, but there are some important ...