Harley Davidson Motor Review - Shovel to M8

The Harley Davidson motor has gone through a lot of changes over the years. From the Knucklehead and Panhead, the Shovelhead and Evolution, and more recently, the Twin Cam and Milwaukee Eight.

In this video, Mike talks about the Halrey Davidson motor from the inception of the Shovelhead motor in 1966 and demonstrates some of the most notable engine changes that have been implemented through these decades.

The Shovelhead Harley Davidson motor was produced from 1966 until 1984. The technology in these motors, and motorcycles in general, is nothing short of old farm equipment. The heads, cylinders, and lifter blocks on these motors were heavy cast iron that held a lot of heat. The motors were not efficient and would need to be torn down for rebuild in as little as 10 to 20 thousand miles.

The Evolution Harley Davidson motor was a huge improvement over its predecessor. Produced from mid 1984 until 1999, it still had a gear driven, single cam but the cylinders, heads and lifter blocks were cast aluminum as opposed to cast iron. The rocker arm and rocker box assemblies were also a major improvement. The Evo had a smaller valve train that was considerably more efficient than the Shovelhead.

In 1999 Harley released the Twin Cam engine. These motors were able to produce even more horsepower. They were more efficient while staying within emission standards. A pair of cams worked great however, cam chain tensioner failure was a nightmare until 2007 (2006 for Dyna). This is when they changed from a spring style tensioner to hydraulic. In 2005, the Twin Cams also changed to a smaller diameter valve stem with a different valve seal and a single “beehive” valve spring as opposed to an inner and outer spring. The Twin Cam motors produced much more horsepower than the Evolution.

The Milwaukee Eight motor is a balanced Harley Davidson motor with a single cam. The heads are even more efficient. There are four, larger valves per head and the intake and exhaust ports are also very efficient.

These are just a few highlighted differences of the Harley Davidson motor throughout the years. Each and every design can be appreciated for its own unique design. From the smooth torque of the Milwaukee Eight to a low idle thumping of an old Shovel. We love them all!

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