Evolution Engine
Harley Davidson manufactured the evolution engine 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).
Twin Cam Engine
Harley Davidson manufactured the twin cam engine starting in 1999.
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 is the largest production Harley motorcycle engine, and it produces 80 horsepower.
The engine remains air-cooled, and uses overhead valves activated by push-rods.
The 88B version of the engine, which came out in 2000, contains counterbalancing shafts to reduce engine vibration.
The Twin Cam 88 is Harley's first new engine since the Evolution SPORTSTER motor of 1986, and their first new Big Twin motor since the original Evolution, released in 1984.
Fifteen years between engines is not really that long a span for Harley.
The Evo's predecessor, the Shovelhead lasted 19 years (with a revision after five), and the PANHEAD lasted nearly as long.
What's significant about the 88 inch is that due to the amount of revision, it has less in common with the Evolution than the Evo did with the Shovelhead.
The Twin Cam 88 is a 45° V-Twin.
The bore has been gapped out to 3.75" (from 3.5"), and the stroke has been shortened to 4" (from 4.25") for a total displacement of 1450cc, 110cc more than the Evolution's 1340cc.
The Twin Cam is named so because, of course, it has two chain-driven cams.
Why they weren't didn't gear-driven, being so close to the crank, we have no idea offhand.
The twin cams are designed to give the push-rods a straighter shot at the rockers (á la the SPORTSTER) for higher potential performance.
The twin cams, with the squarer bore-and-stroke relationship (though still under-square), re-shaped combustion chamber and ports, and new press-fit straight-pin crank should make this new engine a hop-up monster.
The old adage with the Evo engine was, "Bulletproof" until you mess with it."
The new engine should respond much more positively to performance enhancements.
Still it's no slouch in stock form.
In standard, EPA-regulated trim, its claimed peak torque at the crank is 86 ft. lbs. at 3500 rpm. |
Revolution engine
Harley Davidson manufactured the revolution engine starting in 2001.
The Revolution engine is currently used on only one Harley production model -- the VSRC.
While all of the engines previously mentioned are largely the same and represent incremental improvements, the Revolution engine is different.
This engine is water-cooled rather than air-cooled and its V angle is 60 degrees rather than 45.
It has four overhead cams rather than two cams in the crankcase and is fuel injected.
This engine is smaller -- only 69 cubic inches (1,130 cc).
It has a much shorter stroke, allowing it to rev to 9,000 RPM and it produces 115 horsepower.
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