Stage Three Harley-Davidson engines involve any change to any component in the engine. These modifications should only be performed by experienced mechanics with knowledge of performance modifications and engine "blue printing". Special tools are required to perform stage three modifications. V-Twin Café will limit its Stage Three engine information to those combinations that are mostly streetable.
These modifications will provide from 80 to 120 horsepower at the rear wheel of a late model 80 CID Harley-Davidson big twin Evolution engine.

The major difference between Stage Two and Stage Three engines is in the heads. A set of 'ported' heads and higher compression rations are considered essential to reaching Horsepower figures in excess of 80. A successful stage three engine will be well thought out, with all components determined prior to rebuilding the engine. As you view the Stage Three dyno sheets, notice the differences in the power bands. Specifically note where peak torque and horsepower occur. The lower the RPM's are on these figures, the more 'streetable' the engine will normally be.