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68gmsee · 10-17-2017, 04:59 PM

Could be both. Most of the time when I've had valve stem seals go bad, the engine will smoke on startup after sitting for a period of time like overnight. It's not always the case though but they are the easiest to check and/or replace. The last engine I was working on the seals were so bad they crumbled when I removed them for replacing. They were hard and brittle.

You could also try some of the oil additives to see if it can loosen the oil rings if you suspect they are causing some of smoke.

10-17-2017, 04:59 PM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: engine smoking Could be both. Most of the time when I've had valve stem seals go bad, the engine will smoke on startup after sitting for a period of time like overnight. It's not always the case though but they are the easiest to check and/or replace. The last engine I was working on the seals were so bad they crumbled when I removed them for replacing. They were hard and brittle. You could also try some of the oil additives to see if it can loosen the oil rings if you suspect they are causing some of smoke. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...