C5 Tweaker

The dealer installed new rings due to the 2001 oil burning issue. They were kind enough to put on my MTI heads at the same time. #7 cylinder has been oily ever since, and is getting worse.

Facts:

Leakdown on #7 cylinder is one of the best at only 2-3%!

Compression on #7 is on par with the others

No significant blue puff at startup, but plenty of blue/black smoke at WOT - particularly after extended low-speed cruise. Back of car is blackened.

Stock heat plug stay fairly clean, but cooler plug fouls very badly.

#7 seals replaced. No significant benefit. OK if seals are pushed all the way down?


Is re-ringing #7 advisable? Honing required at 40k miles? (Original re-ring job at 12k got no hone per GM procedure)

C5 Tweaker

Anyone? Expert input needed... Thanks

chino_man279

iTrader: (7)

Do you have sealer on the intake rocker bolt for the #7 cylinder? If they are ported heads, I would assume that the rocker bolt is exposed in the intake runner. If GM did not seal it because the stock heads do not need it, the oil could be going in through there. I would take out the rocker bolt and seal it up with thread sealant and loctite. At least you would know it is sealed then. Oil can only come from a few places...rings, rocker bolt(ported heads), valve stem seal, and pcv system. Those are the only things. If it has good compression and leakdown, I would say it is not the rings. If it was the pcv system it would be in all of the cylinders. So this leaves the bolt and the valve stem seal to suspect.

C5 Tweaker

Chino,

I agree. I sealed the rocker bolt with RTV (but I will redo it). PCV has a catch can. The play at the end of the valve stems is at the loose end of operational spec, but not significantly greater than the others.

I am wondering if I should have fully seated the valve stem seals when I replaced them.

Very strange that I can't really observe or measure anything wrong, but still have so much oil...

chino_man279

iTrader: (7)

The inside of the valve stem seal could be scratched and not show that much play. If there is a groove in it from top to bottom this would obviously allow oil through. It also would not wiggle because the seal probably is not worn out, except for a possible groove. Make sure there are no burrs on the valve stem around the retainer groove when you put a new seal on. If there are any burrs or nicks they could damage the inside of the new seal. If you have already taken care of the bolt, then the seal is the only other possibility. I would change out the one seal and go from there.

C5 Tweaker

Fount It!

I took the intake off and observed the entire intake port was unusually clean, but very oil covered. Looking down the port, it had been ported close enough to the spring recess that the material had cracked and started to break through.

Once I took the spring off, I was twice as disappointed to find that MTI apparently found the break-through and tried to seal it up with some brown sealer. Very poor workmanship - shame on you MTI!

Tally TransAm

iTrader: (17)

that sucks, wasnt there another set of mti heads that had this happen, i believe it was cylinder 7 as well, or maybe 5???

mti is a good company though and im sure they will take care of it

edit: heres a link to the other one, this was leaking coolant though

wrencher

iTrader: (2)

Damn! that sucks, sure it'll be taken care of.........

C5 Tweaker

No doubt. I had been guessing for the last 1.5 years that it was likely the warranty re-ring job.

I can't say MTI has not been very supportive in the past. We shall see...