# How do you measure Cam overlap?

## How do you measure Cam overlap?

There are a couple different ways to calculate the overlap of the cam. 1) The easiest way is to add the intake opening times to the exhaust closing time. Seat to seat times (advertised duration) must be used. . 050″ durations or timings will not give the correct overlap.

What is overlap position?

Position available for overlap means the position is available for hire before it is vacated by the current incumbent. For example, Alex will leave his position on 8/15. Mallory will start in this same job on 8/11.

### What is a good camshaft duration?

A 280-degree-duration cam holds the valves open longer than a 260-degree-duration cam. Holding the valves open longer allows more air and fuel into the engine and also allows more to get out through the exhaust. Longer duration (higher number) improves top-end power but almost always sacrifices low-end torque.

How do I increase my camshaft overlap?

To increase overlap, you have to RETARD the EXHAUST, and/or ADVANCE the INTAKE. To reduce overlap, you have to ADVANCE the EXHAUST, and/or RETARD the INTAKE. In a naturally aspirated engine, the extra overlap is called “scavenging”.

#### What is the overlap period in an engine?

Valve overlap is the period during engine operation when both intake and exhaust valves are open at the same time. Valve overlap occurs when the piston nears TDC between the exhaust event and the intake event. The higher the engine rpm, the shorter the amount of time that both valves are open.

How to determine cam duration?

Cam manufacturers agreed on a standard to measure duration so all cams are measured the same way. The idea is to measure duration starting at .050 inches of tappet (lifter) movement. As the lobe lifts the tappet up, when the tappet moves .050 inches, the duration is measured from that point.

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## What is the purpose of valve overlap?

Valve overlap is necessary because as the engine rotates faster, the amount of time spent in the intake stroke decreases. This means the intake valve has to open sooner to give time for the intake air to accelerate and flow into the cylinders.

What is camshaft lobe separation?

Lobe separation is the distance (in camshaft degrees) that the intake and exhaust lobe centerlines (for a given cylinder) are spread apart. Lobe separation is a physical characteristic of the camshaft and cannot be changed without regrinding the lobes.