Harley Davidson camshaft specifications, varying by engine type, include duration, lift, overlap, intake and exhaust lobe centerlines, and lobe separation angle. Valve timing and top dead center specifications are also included in Harley Davidson camshaft specification charts at nightrider.com.
Intake and exhaust duration on the specifications chart refers to the amount of time the intake and exhaust valves stay open, measured in crankshaft degrees. Lift is measured in thousandths of an inch and is how far a valve raises off the seat. Specifications are provided for both intake and exhaust lift, intake and exhaust lift at top dead center or TDC. Power is increased with increase in valve lift, but duration is a coordinating factor.
Overlap specifications, which impact the amount of power an engine can produce, represent the number of crankshaft degrees present when the intake and exhaust valves are open at the same time. The intake and exhaust lobe centerlines are imaginary lines that pass through the maximum point of lift and the camshaft's axis or center of rotation. The lobe separation angle is calculated as the distance between the center line of the intake and exhaust lobes for the same cylinder. Generally, a narrower lobe separation angle means the engine revs faster and a wider angle results in a better idle, increased miles per gallon and reduced emissions.