Mn_Z_Man Posted June 12, 2009 Share Posted June 12, 2009 OK, so I did a valve job to fix a bent valve, and am seeing something weird- lower, but more even compression across all the cylinders. Before I was seeing 175 +/- 5 psi, now I am seeing 155-160. 2 ideas- valve timing is slightly advanced (2 deg on the cam), maybe due to new timing chain guide which is giving a slight inward curve to the tight side of the chain. My other thought was could the carbon buildup on the head and pistons have raised the comp by 15psi? It didn't look that bad, but I don't have much experience to judge by. Obviously its all cleaned up now after. Head was milled 0.003". Valve lash are all properly adjusted, wipe pattern double checked and OK, cam OK, new Felpro gasket. Engine runs OK, maybe not quite as punchy as before. I've put on about 100 mi since the build. Someone on another forum suggested maybe the Felpro gasket having a larger cutout for the L28 engine, as they claimed to have had the same experience, but I can't remember how close the fit was, and they never followed up with a reply. I was hoping the compression would go UP with a shave and valve job. Any ideas appreciated, thanks Eric Quote Link to comment Share on other sites More sharing options...
johnc Posted June 12, 2009 Share Posted June 12, 2009 Valve seats or valves sunk more into the head? Thicker head gasket? Quote Link to comment Share on other sites More sharing options...
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