Quote:
Originally posted by Mr.Fixit
Changing your cam will not change your engine's octane requirement (except at very low engine speeds)
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With all due respect, yes it will. Read this:
http://cochise.uia.net/pkelley2/DynamicCR.html
A long duration cam requires less octane than a 'normal' cam. The reason is that the intake valve remains open until the piston is part way up the cylinder on it's compression stroke. The engine cannot build compression at this time because it's not a closed cylinder. This is why the cam companies will tell you something to the effect of "requires 10:1 compression"; without this much static compression, the engine will not have enough "dynamic compression" to build any low end power. The term "dynamic compression", as used here, refers to the compression the engiine actually sees while running. There is a program on the above website you can download to figure it out. The website also gives a great explaination, which I've barely touched on.
Good Luck,
Dan