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170lbs of compression with 20cc dome on fresh rebuild?
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Posted by: JM317

I just did a complete rebuild on my motor and with a cold compression test I'm getting a solid 170lbs of compression. This is on a mid-ported 265 with 20cc dome and cometic headgasket at 1000ft. I've been searching through similar topics and my compression tester is good (I've removed the 2" extension like I've read about on some testers to get an accurate reading and I also hold the throttle wide open while kicking). So I'm really just wondering if this seems pretty close to what everyone else is getting? I've done 2 heat cycles before this at idle (no riding or throttle varying) and mixed 50/50 race and pump gas just to be on the safe side if the compression was actually higher and I was getting a false reading. Should I expect the compression to go up any also after I ride it a little? Any opinions are appreciated!

Posted by: 86 Quad R

generally, the compression will increase by at least 10 psi after the engine is broke in. i have seen them increase as much as 10%. the psi your getting isn't too bad considering you used a thicker stock replacement gasket.