Harley-Davidson 'Knucklehead' (1936 to 1947)

1936 was the first year for the Model E, which was nicknamed as the "knucklehead" due to the knuckle shape of its engine valve covers. The Model E was a slowly gained popularity, but it was the distance record set by Fred Ham that put the knucklehead Model E into the history books.

The last of the 'Knuckleheads' was produced by Harley-Davidson in 1947. The new versions of Harley's OHV engine were introduced in 1948, featuring chrome-plated valve covers that resembled upside-down cake pans. This was the beginning of Harley-Davidson's "Panhead" era.