Camshaft Selection – Why choosing by degrees is STUPID

In the video below is a completely new way of looking at camshaft selection.

As Gale banks says, you speak to camshaft guys (ie guys that make camshafts) and the only thing they want to talk about is degrees of crank rotation which is a bit ambigious, a bit convoluted, irrelevant and illogical.

This is the video and the gold nugget of advice on cam selection is here

The fundamentals of camshaft selection

The purpose of camshaft selection is to get as much air into the cyclinder as possible.

To do get the air in, the valves need to be open long enough.

When we know how long we want to valves open for, guesswork is removed from the camshaft selection process.

When you think about it, its obvious.

Talking about degrees of camshaft duration obscures the real goal of the camshaft selection process.

Gale Banks calls it “Valve Event Clock Time

When we think in terms of Valve Event Clock Time, it is much easier to understand why a camshaft with a longer duration helps the engine makes more power and why camshaft selection is so important, even on forced induction engines.

If we want the engine to make power at higher rpm, the valve must be open long enough to allow enough air to get in.

When we try to make more power at higher RPM the amount of air we can get into the cylinder per revolution is decreasing because the valves are open for less time.

The two requirements are working in opposite directions. If we want to increase the RPM at which we get peak power, keeping the valve open time per revolution the same at the higher RPM is super important.

To keep the same valve open time at a higher RPM, we need a camshaft with longer duration.

When we think of camshaft selection in terms of valve open time per revolution, it allows us to easily and precisely calculate our camshaft duration requirements. When we know the valve open time we require at our chosen RPM we can select the cam duration we need without any guesswork.

Gale Banks has done an excellent video highlighting the headache that the camshaft manufacturing industry has given us, hopefully his video will turn the tide on camshaft spec sheets, hopefully camshaft manufacturers will start publishing valve open times in their spec sheets rather than forcing the customer to work it out for themselves.

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