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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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#12436 07/20/2004 5:02 PM | Joined: Jul 2000 Posts: 962 Shop Shark | | Shop Shark Joined: Jul 2000 Posts: 962 | I had a rough formula going that equated cranking PSI to static compression ratio. accurate to within about .5:1 CR for a stock engine. Take PSI divided by atmospheric pressure of 14.7 times volumetric efficiency of engine.
Say 160 divided by 14.7 times 80 % gives a static compression ratio of 8.7:1.
This is a really crude formula, cuz it doesnt take true atmospheric pressure, VE or cam timing (dynamic) factors into account. But its fun seeing how off you are when comparing a stock motor to book spec. As stated, I've come pretty close with my "fuzzy math"
chip
Preaching the Hot Rod Gospel according to the 4-stroke apostles:
Suck, Squish, Fire and Fumes
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