LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Exhaust smoke- Valve seals?

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Old Jun 26, 2010 | 01:09 AM
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Chevyguy358's Avatar
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Exhaust smoke- Valve seals?

Ok, so I got the car up and running for the season after troubleshooting some oem wiring issues and retuning it. During on of the tuning "sessions" I let the car sit for 10 mins or so idling and cameback to it overheating. The the fuse had tripped to the electric WP. Now during driving after it warms up it is smoking blue, especially during downshifting etc. This im sure is valve seals that might have gotten a bit warm; Should I drive around on it for awhile and see were it takes me, is there an potential that something like this might clear up?
Old Jun 26, 2010 | 10:07 AM
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I seriously doubt it will clear itself up. If it is still smoking while you are driving then you either have severly damaged your valve seals or <most likely> tore up rings/cylinders. Bad valve seals will usually only smoke upon start up after sitting because the residual oil seeps down into the cylinder as the engine sits, once started, it burns off the oil. Might want to do a compression test and check the state of the cylinders.
Old Jun 26, 2010 | 11:14 AM
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yea, it really only smokes mostly during downshifting (engine braking). Which to my knowledge is usually a valve seal issue. It doesn't seem to smoke in the typical high rpm conditions under a load, which I tend to associate with rings. The motor only has 4,000 on it.
Old Jun 26, 2010 | 11:16 AM
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Ill try a compression test before I assume too much. thanks
Old Jun 26, 2010 | 11:54 AM
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Does it smoke if you let it sit and idle? When the rings did not seat on my current build, the car would start to smoke at idle and the longer it idled, the worse it got.
Old Jun 27, 2010 | 09:30 AM
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hopefully your rings didn't rotate and line up like they did to me...
Old Jun 27, 2010 | 10:07 AM
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Originally Posted by Chevyguy358
yea, it really only smokes mostly during downshifting (engine braking). Which to my knowledge is usually a valve seal issue. It doesn't seem to smoke in the typical high rpm conditions under a load, which I tend to associate with rings. The motor only has 4,000 on it.
Has it been doing this the whole 4k miles or just recently? That would give you a starting point and might be able to rule out some things as well.
Old Jun 29, 2010 | 02:58 AM
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Hasn't done this until just this last week when i was tuning it and let it ldle for a few minutes and found out that that the EWP wasnt functioning and caused the temps to get high. I did happen to be running some cheap oil at the time, I switched back to the 50W Valvoline and it doesn't seem to have much blow by. Though I haven't really taken it out much. I will hopefully be able to take it out tomorrow.
Old Jun 29, 2010 | 05:47 AM
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Cooling system overheating shouldn't cause any valve seal issues.

Smoke on downshift only is pretty much always valve seals. If it were the rings, as in any of the symptoms listed above, you'd have smoke at all times, not just on closed throttle, high rpm conditions. Do a compression test, which I suspect will be normal, followed by a cylnder leakdown test which will probably be normal as well. If both tests are normal, look to the valve seals....
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