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Message: <blockquote data-quote="96blak54" data-source="post: 1486466" data-attributes="member: 14727">My thoughts about maximum variance in compression check?Long as the cylinders are close in compression check, run it! So many variables alter compression checking. Poorly seated valves, ring seal, engine temperature when checking, battery voltage, fuel or other liquids in the chamber.Here is a copy/paste suggestion from popular hotroding"If you find one or more cylinders are below the 10 percent range of the others, squirt a little oil down the cylinders and try again. If the pressure comes up significantly, the problem may be worn piston rings. If the pressure does not come up on retest, the issue may be with the valves or the head gaskets."So with not knowing your compression checked numbers, lets say most were roughly 150psi and a few cylinders touched 135psi. Ten percent of 150 is 135 and considered acceptable. I feel 10percent is to tight for a high mileage engine especially for a modular with pi heads knowing how a high mileage pi headed exhaust valve looks. I have yet seen one with a good machined seal. The exhaust valve seal is pitted and beat up looking. Also engine temp needs to be hot when checking compression especially modulars. Cold lashers can keep the valves from sealing completely. This could be only .005".  Its not a complete seal, but will raise a compression gauge.You also asked what is more important, compression deviations or squish kiss.Pursuing squish means unbolting heads. Try to figure out why your engines compression numbers are different before unbolting them. This way you can potentially correct the problem....it could be bad valve sealing where a simple valve lapping will bring it back to a good seal.</blockquote>