Camshafts blow my mind


Jul 28, 2018
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I am looking into how the duration and LSA of a cam effects the dynamic CR of an engine. It is absolutely fascinating. Then you can also advance or retard the cam to effect the dynamic CR as well. I wish David Freiburger would do a test on engine masters comparing the same engine with the same dynamic CR but with different cams.

I feel like the test would be wildly expensive though. Wouldn't you want to use the same heads and head gaskets so the quench would be the same? Lets say it was an ideal .030 of quench. Wouldn't the best A to B test involve using pistons with the same compression height but with different sized +/- CC's to get the Dynamic CR the same?

So lets say we took two different cams in a 446ci mopar. The internet tells me that 8.5:1 is on the high end of dynamic cr you want to be at for 91 octane so lets just use that.

I wonder if the average power across the RPM band would be the same for say a cam that has a duration of 262/270 @.050" lift w/ an LSA of 108 compared to a cam that has a duration 228/236 @.050" w/ an LSA of 112. For the sake of the argument the lift is the same. Lets also say you took the highest average across a 4,000 rpm sweep.

But wouldn't this test not prove anything except that the bigger cam makes more power over-all because the engine that rev's higher has a higher "VE"? You would have to use a tunnel ram because a dual or single plane would favor one cam over the other.

Are all these questions stupid because the average person is just going to stick a cam in their engine or have someone else do it and not think twice about it? Does the change in CR by a point or point in a half by just changing a cam in an engine really just not matter?

Anyway thanks for listening. Watch is slow tonight and chat on the classified network is quiet out here. I guess I am thinking about seeing all the dyno sessions where people make big cam changes and the dynamic cr changes and I think if the change in dynamic cr really even matter.


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FCBO Gold Member
May 26, 2020
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Toronto Canada
Cool idea. What i see on all the dyno testing is they start the power band at 3000/3500. Our/my big old C-body is all in by 4000 at most.
Love to see power increases from 1200 to 4000 rpm.