Need Help-Low Compression in One Cylinder

[Jack Zupan]

I have got a problem I can't diagnose yet. I have a 351W with 2V Cleveland heads in my Cobra. I put an MSD setup in the car a couple months ago and noticed a burble at idle from the left sidepipe. I think the MSD made it more noticeable but that could be my imagination. Except for the idle the car seems to run fine. The burble is not at every stroke but only every so often, maybe every three to four cycles. I pulled the plugs on the left side the of the engine bank and found the number 5 plug to be black and the insulator also had a black carbon coating. I guess there must be oil burning in that cylinder. The other three plugs looked like I just put them in yesterday. I did a compression check and only had about 60 pounds in that cylinder. I measured 185 lbs last time I did a compression check which was probably last year. Number six had 172 lbs in it. I pulled the valve cover and can find nothing wrong there. Springs are intact and pushrods look straight. The valves move up and down when they are supposed to. There are still some other possibilities but I don't know where to look next. So I ask some of you engine gurus out there what would you look at next. I don't want to pull the head unless I have to but that looks like the next step to me. Any ideas from you guys?

Thanks,

Jack Z