Which Harley-Davidson engine was known as the “Ironhead”?

The Harley-Davidson Sportster engine produced from 1957 to 1985 was known as the Ironhead.

The nickname referred to the engine’s iron cylinder heads, distinguishing it from later Sportster engines with aluminum heads. The Ironhead was an overhead-valve V-twin and formed the mechanical heart of the Sportster family for nearly three decades.

Ironhead Sportsters were offered in several displacements, including 883 and 1,000 cubic centimeters in later years. They became associated with a relatively compact, performance-oriented Harley-Davidson motorcycle.

The Ironhead was replaced by the Evolution Sportster engine in 1986. The term therefore identifies a specific Sportster engine era, not every engine used in the Sportster family.