Harley-Davidson Engines

Knucklehead, Flathead, Shovelhead, Evolution and More: Harley-Davidson Engines since 1909

If you ride a Harley or would like to someday, knowing a thing or two about the evolution of the company’s iconic V-twin engines is pretty important. You’ll need that knowledge to help you maintain your street cred, or at least keep you from needing to lip-sync the song Tequila in a biker bar. (If you don’t get it, don’t ask.) Want to learn the actual differences between a Knucklehead, Panhead, or Twin Cam 96 and why you should care? Read on.

The Harley-Davidson V-twin engine is nearly as storied as the company that created it. The angled engine cylinders set at 45 degrees first appeared commercially on Harleys in 1909, but the design was a flop at first. Only a few dozen were ever built. The automatic intake valves were designed for single-cylinder engines and caused problems with the flow characteristics. It took some tweaking, the addition of mechanical intake valves, and a new frame before the V-twin found success in 1911.

A Brief History of Engine Names

Through the years Harley motors have increased in displacement and sophistication, but the Big Twins have always kept some things in common. All Big Twin Harleys have been longitudinally-mounted, air-cooled, 45-degree V-twins with large displacements. Not all Harley models have been Big Twins, but most of the longest running and most memorable are. Several Big-Twin engines earned nicknames based on their appearance while others go by their official factory names.

F-Head (1911 to 1929)

These were some of the first V-twins, and they get their name from the shape of the intake tract determined by the location of the valves.

Flathead (1929 to 1939)

Harley-Davidson Flathead Engine


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