The Shovelhead engine is a motorcycle engine that was produced by Harley-Davidson from 1966 to 1985, built as a successor to the previous Panhead engine. When the engine was first produced, the Shovelhead had a shallower combustion chamber, larger valve drop for both intake and exhaust, better porting, and stronger valves and pistons. This gave the new engine an extra 10 horsepower, along with a different appearance. The engine gained the nickname “Shovelhead” due to the look of the rocker heads having the appearance of an old coal shovel that was flipped upside down, giving the appearance of a shovel. While the engine did have problems earlier in its timeline, the new and improved motor gave Harley-Davidson a 26% sales increase.