Low cranking compression. Possible causes?
Low cranking compression. Possible causes? I have an 08 L92 in my car, and it's always been lazy below about 3500 rpm. We took it to the track last weekend, and were disappointed to say the least. It went a 2.0 60' and a 7.45 @ 102 mph (1/8th). The car was 3585 lbs with me in it and we were on 9#'s of boost with pump gas. My buddy thought maybe the cam was retarded a few degrees, so we degreed it last night only to find out it was correct. Other than the factory L92 tensioner thing lost that metal "spring" in it. The cam is .598/.596 231/244 on a 114+6. I did a compression test on it before we degreed the cam, and got about 120-125 on all but one cylinder. I think it was #5 had 140 psi on it. I'm going to do a leak down test this afternoon, but what else could/would cause such a low cranking compression? Maybe bent rods, rings, valve seats?
Timing was at 12* total. I'd have to go back to the logs for the AFR.
I know there's a difference between SCR and DCR, but this cam only has about 9 degrees of overlap. Is the cam bleeding off the compression, or is there something else wrong?
I know there's a difference between SCR and DCR, but this cam only has about 9 degrees of overlap. Is the cam bleeding off the compression, or is there something else wrong?
If it’s not bad lifters, bent push rods, it sounds like you hurt it. Having one cyl much higher than the others rules out cam degree. Everything points towards damaged rotating assy/HG/valve sealing issue. Time to pull things apart!
