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Discussion Starter #1 (Edited)
I have been chasing some engine tune issues and decided that I should check the engine compression to make sure that the problem is not originating there. The test results are based upon two sets of measurements taken with a warm (not hot) engine with the throttle held open. The average of the eight measurements came out to 165 psi with a variation of +/- 2.5 psi from the highest to the lowest measurement.

The Volvo service manual sets out compression test results as 170 -200 psi, so I am below the lower value. However, I have a B20 F head gasket in the engine which lowers the compression ratio. I had measured clearance volumes on the engine at the time of assembly. Based upon the different clearance volumes with the E and F head gaskets, I did a back of the napkin calculation and estimated that the increased clearance volume would reduce the ideal compression test results down to the 164 - 193 psi range. My back of the napkin analysis is based upon an isothermic compression cycle with the air starting off at ambient (adiabatic would probably be closer with some provision for air heating due to a warm engine). My napkin calculation puts the test results at the bottom end of acceptable.

Has anybody done a compression test on a B20E with the F head gasket and if so, what were your results like?
 

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I think that compression tests are very good for comparing cylinders in an individual engine, but the absolute numbers are not all that significant. There are too many variables, including cranking speed and elevation (cam selection as well, but yours is stock). I don't know how much the .020" thicker gasket would change the readings, but I'd say you're in fine shape with that small a variation between cylinders.
 

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Discussion Starter #3
Thanks Phil. My initial reaction, based upon the low cylinder to cylinder variation, was the same. Barometric pressure at the time of the test was right around 100 kPa so that eliminated that variable. Its also possible that my no-name compression tester could be out of calibration.

I will leave it for now and check it again after a few months of operation.
 
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