All of this information is very helpful when degreeing in your cam. Simply plug in the information in the yellow boxes (duration numbers at 0.050, lobe separation angle, and even advance if you like) and the program spits out not just the overlap, but also the exhaust and intake centerlines, and even how much tappet lift you should see at 0.050. It is a Microsoft Excel worksheet, so it should work with most Windows-based computers, and it can tell you much more than just your overlap. You can figure it out yourself with a little math, but an easier way is to use the 'Overlap Calculator' Comp Cams provided us while working on this story. But many don't specifically tell you how much overlap is ground into the cam. And as you might expect, a greater LSA reduces overlap (because it spreads the intake and exhaust lobes apart) while a smaller LSA increases it.Īll reputable cam manufacturers send a cam card with all their camshafts that include most of the pertinent information you will need.

Most performance cams use an LSA in the 110-degree range. It is measured in degrees of crankshaft rotation. The LSA is the distance between the centerlines of the intake and exhaust lobes for a single cylinder. The second option is to change the lobe separation angle (LSA). When that happens, the piston starts moving back up the cylinder and pushing air back into the manifold. What you have to avoid is extremely long intake duration where the intake valve is held open past bottom dead center. Shortening the duration-and the amount of time the valves are open-generally reduces overlap.

The first is to change the duration that the lobes hold the valves open. Overlap can be changed by adjusting the camshaft in one or two ways. So the trick is to figure out how much valve overlap you can have and still meet your minimum vacuum number to pass inspection.

Chevy 350 performance cam