I'm having my 1986 CJ-7 rebuilt. It has the 4.2 engine. It was a complete engine rebuild and it's smoking from the exhaust. The mechanic has had a lot of experience with jeeps but is at a loss for why. He said that for some reason the spaces on the rings keep getting aligned after it's reassembled and run which is allowing oil past the rings into the cylinder. He's checked all the machining that was done and it's all within specs. He's also checked with other mechanics to see if they've ever run into this problem to no avail.
Figured I'd throw this out there to see if anyone else has run into this before and have an idea why. He said he's going to try a different block and if it's still smoking he's going to give it back to me at no cost for any work done since he hasn't been able to solve the problem.
Last edited by PJCJ7; 04-13-2012 at 11:26 PM..
Reason: typo and further info.
The only thing I could imagine that would cause this would be the cylinders being out of round.(and. yes, I'm pulling that out of thin air. I truly have no clue...) Machining would have corrected this.
[QUOTE=gpets;10833372]...it is perfectly acceptable to take a sawzall to anything you can't figure out, that is how we all learn.[/QUOTE]
A completre engine job would have used new pistons right,maybe they got the engine kit wrong,a newly bored and honed block should be ok if it is within specs,I would check to see if pistons or rings are right.
i would say the rings are wrong. sounds like they don't have enough tension against the walls causing them to spin. And...... if the rings are wrong what about the pistons? Has your mechanic actually pulled any pistons out? Do you have access to the part numbers of the rings and pistons used?
1981 Jeep CJ7 4.0 HO, AX-15, D300, D30, D44, SOA
1977 Chevrolet C/10 step side 454 TH400 3.73 posi
I'm not sure if it's happening on all the pistons. I'll ask him. He's said he's staggered the rings when he placed the pistons into the engine but when he's pulled them out after running the engine, and it is still smoking, the gaps in the rings are aligned again. He's tried upgrading to better rings with the same result. He's had to pull the head off several times after reassembling it because it was still smoking. He's expressed that he's never seen this before and he's at his wits end trying to figure it out. Trying a different rebuilt block is his last attempt to correct the issue. I'll also double check about whether he's got the right pistons and rings. As far as mileage, it's well over 100k but like I said, it was just completely rebuilt.
Thanks for the responses, really appreciate the help.
Was the engine smoking before? and exactley what was installed and what was machined? does it smoke? has the engine been run under load yet? somtimes it takes loading engine to seat rings. what hone method was used on cylinder walls? and who rebuildt head what valve stem seals were used?
So I got the jeep back. He replaced the block and it's not smoking anymore. Unless the machine shop screwed up my block when they did the work I can't really see why it made the difference. My mechanic is going to have my old block checked by a different machine shop.