Turbo or Valve Guides?

L-body '86 log with MP computer and '88 roller cam/followers. Runs great, but smokes on deceleration (none noticeable on accel.). I did recently refresh the bearings and rings and replaced just the valve seals. The head has never been reworked. I've checked that the oil drain line from the turbo is not blocked and is flowing oil to the block (verified this line also). I dont have a picture of the plugs at this time, but they do have a bit of dry fouling/deposits on one side of the electrode. Pistons do appear to have some oil on top. Is there any way to say for sure what the issue is before I purchase parts?

Decel = high vacuum in intake manifold. Worn seals or valve guides could be the culprit but it could certainly be a compressor cover seal as well. The TI log style sees vacuum in the compressor side of the turbo also.

Chris-TU

I had one with guides popping off that smoked like a train every time on decel. If you don't see oil in the cylinders at all, it could be sucking oil through the exhaust side and would be hard to say either way, valve seals, guides or the turbo. You can pull the valve cover off and see if there is anything obviously wrong, may prove to be useful.

Thanks guys. I popped the VC off and nothing looks obviously wrong. I’ll see if I can get a look in the cylinders. I have a limited budget, so I’m hoping I can find the right direction to point the $$


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I should note that I have about 95% of the parts needed for tII conversion, including a new turbo (I believe sourced from TU, awhile ago, I’ll have to check the receipts). Should I bite the bullet and just do that (and get the head fixed up)?


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cold starts and off idle tend to give you an idea if it is valve stems.

start car. drive it a few miles.
idle for 2-3 minutes. ( might get a little smoke at idle and get worse over the 2-3 minutes of idle.)
then stab the gas while sitting still.

if you get a BIG cloud from that its the valve stem seal 99%.
they draw in oil during idle from the high vacuum. and when you hit the gas it sucks it all in.

Also when you pull the valve cover.
look down in the springs and check all the stem seals.
pay extra close attention to the EXHAUST seals..

these little turds love dropping exhaust valve guides.
and this causes the stem seals to not have enough to grab onto to stay in place..
if you guides dropped. ( very likely) the new stem seals are not staying on the guides causing your leak.


my last turbo that went would lay a HUUUGGEE smoke screen after being in boost for 4-5 seconds. then decelling.
massive smoke cloud..

T2 I had that went bad would fog the intersection on decel, blow a huge cloud of smoke on take off but then almost nothing while steady cruising.

Pretty much does all of those things. Decision made, dealing with the head, and probably tII at the same time. Thanks for the advice!

Might have to make a thread for it...


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