The Harley-Davidson Big Twin has a look and sound that is unique among motorcycles.
Harley Davidson has been improving its Big Twin engines since the first side-valve 74-cubic-inch engine was introduced in 1922. The Big Twin series has progressed through the Knucklehead, Panhead, Shovelhead and Evolution engines to the Twin Cam series, which was produced from 1999 to 2006. While Harley riders usually prefer the design of their first personally owned Big Twin, they generally concede that each progressive redesign has been an improvement over previous designs.
The Twin Cam 88 has a cylinder bore of 3.75 inches and a piston stroke of 4 inches, rendering a displacement of 88.4 cubic inches or 1449 cubic centimeters. This is an increase in bore size, but a decrease in stroke compared with the previous 80-cubic-inch Evolution engine’s 3.5-inch bore and 4.25-inch stroke.
The 1450-cc Harley Twin Cam 88 engine is rated to produce 80 horsepower at 5200 RPM, and 82 foot-pounds of torque at 3500 RPM.
Valvetrain Changes from Previous Models
The 1450-cc Twin Cam 88 engine has a single overhead cam for each cylinder. The cams are driven by a silent chain. This is in contrast to all previous Harley Davidson engines, where the cams were located in the crankcase and drove the valves through pushrods. This overhead cam design allowed a more efficient combustion chamber design with a 9-to-1 compression ratio, providing a 10 percent power increase over the previous Evolution engine.