always89

So, did a compresion test, and all is good except for #1. 30psi. So, we are going to milk this engine for a while more while we order a Jasper. IS there a product that can be used to "pour" into that cylinder to milk a bit more compression?

Donnie_K

probably just needs a head gasket. if it's not an 00-01

always89

Dont think its the gasket. No oil in water or vise versa. Next cylinder has strong compression, and there is nothing escaping the outside. Where would the pressure be going?

CodeXJ

Pour a cap full of oil into the cylinder and test again. If the compression goes up, rings. If it doesn't? Head gasket or valve issue.

I'm going to lean with valves, though. Usually if it's rings, then at least one other cylinder is going to have low compression due to wear as well. Valves can go bad due to a lot of issues, my brothers ZJ is a 7-cylinder at current due to an overheat that resulted in his valves not sealing correctly on one cylinder. He's been like that for almost a year and a half now. If it is a valve problem, fixing it should be as simple as removing the head and taking it to a machinist. Maybe $500 total after reassembly and a new head gasket?

Bustedback

I'm guessing it would be a valve issue, but it could be rings. Kind of strange to have just one cylinder down if it were rings, but it could happen.

always89

Im buying into the valve theory. I did pull the cover, and everything LOOKS to be right, but when the weak cylinder is at TDC, there is NO lash in the rocker. Maybe its to tight and holding the valve open? Whatcha think?

Bustedback

They're hydraulic lifters, so I don't think that would be the case. But if the valve seat was really worn, I guess the lash could be tight because the valve tip would be higher.

FourWinds

If you've got a lot of crankcase blow-by, I say it's rings. If you don't have much blow by, it's more than likely a valve or head gasket.