In 1966, Harley-Davidson replaced its V-twin Panhead engine with the V-twin Shovelhead. This would be Harley's motor for the next 18 years until the Panhead yielded to the Evo, or Evolution, engine --- also a Harley signature V-twin configuration.
Shovelheads were twin-cylinder, air-cooled, four-stroke motors. The V was arranged front-to-back. The cylinders were aligned at 7.22 degrees C around the crankshaft. While the bottom half of the Shovelheads were the same, they were made in two sizes: 75 and 80 cubic inches.
The 80-inch, 1,310-cc engine had a bore diameter of 3.498 inches and a stroke of 4.250 inches or 88.85 x 107.95mm. Compression remained fairly low at 8:1 and 7.4: 1 on post-1980 models. The larger, 80-inch engine was known also as the FLH from its inception until 1978. The smaller 1,200-cc unit was known as the FL. The FL and FLH designations were dropped in 1978.
Early 80-inch/FLH Shovelheads produced a maximum 66 horsepower at 5,600rpm. From 1970 to 1984, maximum horsepower dipped slightly to 62, peaking at 5,400rpm. Horsepower dipped to 60 in 1978 to 1980 models, climbing to 65 in 1981 through 1984 versions.