Twin Cam 88 – (aka “Fathead) was manufactured from 1999 – 2006. The Twin Cam gets its name from the fact that it has two cams in the crankcase to activate the valves. At 88 cubic inches (1,450 cc) of displacement, it was the largest Harley motorcycle engine at the time, and it produced 80 horsepower. The engine was air-cooled, and used overhead valves activated by pushrods. The 88B version (2000-2006) of the engine, which came out in 2000, contains counterbalancing shafts to reduce engine vibration.                                                                                                                                                                                                        

Evolution – Manufactured between 1984 and 1999. Displacement is 81.8 cubic inches (1,340 cc), and the engine produces 70 horsepower. Although the Evolution 1340cc is no longer in production, the Sportster model line of motorcycles receives Evolution engines with 883 cc and 1200 cc displacements (manufactured 1986 to present).

Shovelhead – Manufactured between 1966 and 1985. Shovelheads displaced 74 cubic inches (1,200 cc) and produced 60 horsepower from years 1966 to 1977.  From 1978 to 1985 they were 80 cubic inches.

Panhead – Manufactured between 1948 and 1965. The panhead also came in 60 cubic inch (990 cc) and 74 cubic inch (1,200 cc) variations and produced 50 and 55 horsepower respectively. Big differences between the knucklehead and the panhead included aluminum heads on the panhead and internal oil lines, as opposed to external lines on the knucklehead.

           Knucklehead – Manufactured between 1936 and 1947. The knucklehead came in 60 cubic inch (990 cc) and 74 cubic inch (1,200 cc) variations able to produce 40 and 45 horsepower respectively.

          Flathead – Manufactured between 1929 and 1974. Flatheads did not have overhead valves. Instead, the valves ran alongside the engine and opened upwards into a chamber beside the combustion chamber. The advantage of a flathead was simplicity — no pushrods or rocker arms, and the head was a simple casting with a hole in it for the sparkplug. A typical Flathead engine had a displacement of 45 cubic inches (742 cc) and produced about 22 horsepower.

      1911   Harley Twin Energine start up and run in !