Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - compression ratio vs. pounds per square inch.
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Old 03-17-2013, 08:55 AM
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The CC-268H single pattern camshaft in my 455 had .454" valve lift, 110* LSA, 39* valve overlap with 215 PSI cranking pressure.

The Melling SPC-8 Ram Air IV camshaft in the same engine had .480" valve lift, 114* LSA, 87* valve overlap, and 170 PSI cranking pressure.

I first used a CC-268H "RV" camshaft in my 455 Pontiac engine but the CC standard hydraulic lifters were noisy. After about the first 400 miles, I switched to a Melling SPC-8 Ram Air IV camshaft and Melling JB-951R limited travel lifters. That change resulted in a quiet valve train and reduced cylinder pressure.

I suppose the valve events made the difference in cranking cylinder pressure. I do not recall what the valve events were.
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