In this example, there will be overlap. 8° + 13° = 21° of overlap. Keep in mind the opening and closing events are listed at 0.050 in. of Valve Lift. So, the calculated overlap is at 0.050 in. True overlap will be slightly more. Can I adjust the amount of overlap? You can't adjust the overlap on your camshaft. You will need a New Camshaft.

To advance or retard a camshaft is to change the alignment between the camshaft and the crankshaft. When a cam is installed "straight-up," the imaginary centerlines of the two shafts line up exactly. Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline.

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.

It also allows more exhaust to escape. This creates more power. (It is why a camshaft's RPM Range is based on its duration.) However, at low rpm, the open valves reduce the pumping pressure of the piston. This results in lower cylinder pressure and less low-end power. Long duration camshafts also create more Valve Overlap.

Valve timing events set Duration, Lobe Separation, Advance, and Overlap. Exhaust Valve Opening (EVO) EVO controls the evacuation of combustion gasses. This is also known as blowdown. Most blowdown occurs before BDC because of residual cylinder pressure. Opening the valve a little earlier or later is a compromise.

Camshaft #2 has excellent top-end horsepower. However, it requires at least 10.5:1 compression, a 3,500+ stall converter, and rear-end gears to get the best performance. To get the best performance from your engine, match the intended rpm ranges of the following parts as closely as possible: Camshaft; Carburetor; Intake manifold; Cylinder heads ...

**Remember, the camshaft rotates once for every two rotations of the crankshaft.** How is it listed? The following table outlines an example of camshaft timing at 0.050 in. BTDC = Before Top Dead Center; ATDC = After Top Dead Center; BBDC = Before Bottom Dead Center; ABDC = After Bottom Dead Center

Some valve overlap is needed to maximize the scavenging effect. So, all high-performance engines will have some reversion, especially at low rpm. However, it can be minimized. Improve Your Exhaust Flow: A stock exhaust can have 8 psi (or more) of backpressure at 6,000 rpm. Log-style manifolds can cause exhaust from one cylinder to be sucked ...

Installing a Performance Camshaft can add a lot of power. However, a common side effect is less vacuum. For vehicles with power brakes, this means a hard pedal, which isn’t fun to drive. Why does this happen? Upgrading the camshaft increases performance through Valve Overlap. This is good for power and makes the lopey idle racers love.

Effective scavenging is how you make more power! The more valve overlap you have, the more important scavenging becomes. At the bottom of the power stroke, the cylinder is full of exhaust gases. During the exhaust stroke, the piston has to push the exhaust out. Any backpressure (restriction in the exhaust system) requires the piston to push harder.