Camshaft Technology
Understanding Lobe Separation Angle (LSA)
If you look at enough cams, you might begin to notice that cams with the same duration and lift can have different performance characteristics when installed in similar bikes. At first glance, it may seem difficult to explain. A difference in the lobe separation angles (LSA) of the cams can explain the difference. Here is a summary of what general conditions you could expect for the engine if the LSA is made wider or narrower.
Condition Wide Separation Angle Narrow Separation Angle
Overlap Decreased Increased
Low End Power Higher Lower
High End Power Lower Higher
Detonation Potential Lower Higher
Intake Events Later Earlier
Exhaust Events Earlier Later
Overlap Decreased Increased
Manifold Vacuum Higher Lower

LSA is the Lobe Separation Angle or the number of degrees between the intake and exhaust lobe centerlines. The LSA has a direct relationship to amount of overlap on a cam. Cams with identical duration and lift specifications can have very different LSAs. Generally speaking, a wide LSA will produce greater low end torque and a narrow separation angle will produce better top end power. For any given LSA, an engine will give similar torque curves and peak torque RPMs even with different overlaps. Refer to the LSA table above to determine how an increase or decrease in LSA is expected to change the performance of the engine.

Intake Lobe Centerline is an imaginary line that passes through the camshaft rotation axis and the point of maximum lift of the intake lobe. Changing the lobe centerline without changing the duration can increase or decrease the point at which intake events take place during engines cycles. Increasing the intake lobe center line from 104 to 106 degrees is considered retarding. All events will take place later in the engine cycle. Retarding the cam causes the intake valve to open and close later. This will reduce cylinder pressure which reduce the low speed performance of the engine. Remember that advancing or retarding a cam effects both the intake and exhaust. Do not advance or retard a cam by installing the cam with the timing mark offset by one tooth. One tooth on the timing gear is about 17 degrees.

The cam can be offset by pressing off the timing gear and re-installing it. This should only be performed by experience performance mechanics or by the manufacturer. A better solution is to use Crane Cams High-Roller series of camshafts with an offset keyway timing gear than can be advanced or retarded 4 degrees.

Exhaust Lobe Centerline is an imaginary line that passes through the camshaft rotation axis and the point of maximum lift of the exhaust lobe. Changing the lobe centerline without changing the duration can increase or decrease the point at which exhaust events take place during engines cycles.