In this short article, I am going to talk about lobe separation angle.
Definition & Description
“If you drew a line that divided the intake lobe in half right at the point of maximum lift, and then did the same to the exhaust lobe, then measured the distance in cam degrees between the two, that would be the lobe separation angle. On engines equipped with independent intake and exhaust cams, the LSA is adjustable. But for small-block Chevys (like the LS applications in this story), the LSA is ground into the cam. It is possible to advance and retard the timing events, but the distance between the centerline of the lobes will remain constant.”
The Lobe Separation Angle (LSA) is the distance between the centerlines of the intake and exhaust lobes on the camshaft. It is measured in degrees of camshaft rotation.
According to the Comp Cams catalog, “The lobe separation angle (LSA) is equal to 1/2 the angle in crankshaft degrees of rotation between the maximum exhaust valve lift and maximum intake lift.”
How is it measured?
You can calculate the LSA using the centerlines of the intake and exhaust lobes. (This information should be listed on your Cam Card. If not, you can find them using a Dial Indicator and Degree Wheel.)
The formula for LSA is:
Intake Centerline + Exhaust Centerline ÷ 2
For example, if the intake is 107° and the exhaust is 117°:
107° + 117° = 224°
224° ÷ 2 = 112° (LSA)
How does it affect performance?
Combined with Duration, the LSA determines Valve Overlap. This overlap has a significant impact on Engine Vacuum and idle quality.
- Camshafts with a “tight” LSA (106° – 109°) will usually have more overlap.
- Camshafts with a “wide” LSA (110° – 118°) will have less overlap.
I hope you liked this post. It was influenced by a post on Summit Racing.
We have a few more articles about camshafts, like Camshaft Duration, Camshaft Lift, and Camshaft RPM Range.