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if i have a 9.0:1 compression ratio what should the compresson checker gauge read like psi? i think im getting about 120 is that right?
 

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I was taught that it's not possible to equate "PSI" directly with "Compression".

It has been said that typically lower psi readings like yours usually accompany low compression engines and the opposite for higher compression engines...............

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Jimmie's right on this one. Too many variables ("unknows") needed to make the calculations follow through to calc. the compression ratio when just taking readings from a PSI gage.
 

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Compression ratio is nothing more than a mathematical formula. It is the total volume of the cylinder with the piston at the bottom of the cylinder vs the volume of the cylinder with the piston at top dead center. Total volume includes the combustion chamber area.
 

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Engines with high duration cams bleed off compression at cranking speeds so they would show lower psi compared to the same engine with the same compression ratio but with a stock cam. So no you cannot assume higher compression readings mean high compression ratio.

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