The Knucklehead is a specific type of motor that was once used in motorcycles built by the famed Harley-Davidson Motorcycle Company. The Knucklehead was featured in motorcycles that were produced between the years 1936 and 1947. The Knucklehead was one of the first Harley motors to be built with the company's signature V-Twin engine design.

The Knucklehead engine was available in both a 900cc and 1200cc displacement. The engine was so-named because its heads resembled the knuckles on the top of a hand. The Knucklehead also marked the first time Harley-Davidson would produce a product that trumped their biggest rival, the Indian Motorcycle Company.

The Panhead engine was the next line of engines produced by Harley-Davidson. These engines were manufactured between the years of 1948 and 1965. The Panhead also displaced either 900cc or 1200cc, but it delivered slightly higher horsepower than the Knucklehead.

In 1965, the company started building bikes with the Shovelhead motor. Like its predecessors, the Shovelhead engine has a displacement around 1200cc. However, around the year 1978, the engine's capacity was bumped up to about 1310cc and remained at that level until it was replaced by the Evolution engines.

Since all of these engines were built on the same basic design, it's hard to say which is best. It all depends on what you're looking for. If you're going strictly for appearance, most motorcycle enthusiasts believe the Knucklehead looks the best, whereas a Panhead will give you the same look with a slightly better performance. However, the compact design of the Shovelhead makes it ideal for installing in most aftermarket chassis.