Thread: How low is to low on compression

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What would be considered low compression on a SBC 350 cu/in motor that is pretty stock, and how much deaviation between cyl's. is acceptable?

Hudnnn:

On the newer low compression, smog, motors I like to see 110 to 125 psi on a compression check. I have had some very high milage motors, sbc, that were in the 90 to 95 psi range and they still ran well, although used some oil. Generally less than 10% differance between cyls. If one or more are lower than that, you can squirt some oil in cyl and retest, if compression comes up it indicates worn rings, if not valves or head gasket. Two cyls next to each other with low compression usually indicates bad head gasket. Also best to check after engine has been warmed up to operating temp. It is a more reliable test, as you are checking compression pressure in a close to operationg enviroment. Hope this helps.

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