HISTORY OF THE HARLEY ENGINE
The 45 cubic inch V-twin engine (later to be known as the "flathead") is introduced on the D model. The engine proves to be so reliable that variations of it are available on Harley-Davidson motorcycles as late as 1973.
Harley-Davidson introduces the EL, an overhead valve, 61 cubic inch powered bike. With increased horsepower and bold styling changes, the motorcycle quickly earns the nickname of "Knucklehead," due to the shape of its rocker boxes. The same year, the Motor Company introduces a 80 cubic inch side valve engine.
New features are added to the 61 and 74 overhead valve engines, including aluminum heads and hydraulic valve lifters. Also new are the one piece, chrome plated rocker covers shaped like cake pans. The nickname "Panhead" only seemed logical.
The first of the "Shovelhead" engines is introduced on the Electra-Glide models, replacing the Panhead.
Harley-Davidson unveils the 1340cc V²® Evolution® engine on five models including the all-new Softail®. The result of seven years of development, the Evolution engine produces more power at every speed, runs cooler, cleaner and is oil-tight. Also witnessed is the debut of the Softail design and its trend-setting method of "hiding" the motorcycle's rear shock absorbers.
The Touring and Dyna motorcycle families receive the new Twin Cam 88® engine.
Harley-Davidson introduces the liquid-cooled Revolution X™ powertrain on the Harley-Davidson Street™ 750 and Street™ 500 motorcycles - the first all-new platform from Harley-Davidson in 13 years.