Do they all blow a little white cloud when they start?

[Gotenntitans]

My white & black '90 GMC Sierra, the one that was stolen, always blew a little cloud of white smoke upon cranking after sitting for a few hours. My '90 Chevy Sport does it too. My dad's '87 GMC Sierra squarebody does not.

Is it something with the OBS V-8's, or have I just been lucky enough for that to happen to both that I've owned?

[Just call me Sean]

That's usually valve guide seals.

[special-K]

The bad guide seals smoke will not be pure white, which means coolant in combustion chambers, but the smoke may described as white with nothing to compare but clear air. When it's cold there can be vapor from the exhaust on start up. Burnt oil from valve seals will actually be light greyish blue. That's not a biggie for quite a while. The worse they get, the more frequent it will puff smoke, such as anytime you come off idle. By then you will notice some extra oil consumption. If it is steam from coolant, you will notice milky residue in the oil fill cap... once it's been a while or gotten worse. When it's real bad you'll see coolant bubbling in the radiator

[Gotenntitans]

Thanks friends. This new to me '90 Sport blows a puff upon startup and it's got a very strong smell to it. Like burnt oil. When I rev up the engine, though, it doesn't blow any more smoke so I guess that's not a bad thing. It's not using any oil between changes.

It did sit a while......it's only got 13K miles on it. Had 8K when I got it last May.

[special-K]

Definitely sounds like valve guide seals. They'll give you time to fix them, but they will get worse to where more oil will be consumed and it will smoke more often and longer. Like sitting at a light and pulling off, it will leave a cloud the first 50'. Eventually it will foul plugs. They probably got dried out while sitting. Easy enough to fix with heads left on.

What's happening is oil is leaking past the seals, down the guides into the combustion chamber while parked. Then burned off when you start it

[SCOTI]

Originally Posted by special-K

Definitely sounds like valve guide seals. They'll give you time to fix them, but they will get worse to where more oil will be consumed and it will smoke more often and longer. Like sitting at a light and pulling off, it will leave a cloud the first 50'. Eventually it will foul plugs. They probably got dried out while sitting. Easy enough to fix with heads left on.

What's happening is oil is leaking past the seals, down the guides into the combustion chamber while parked. Then burned off when you start it

Exactly. So when you start the motor (or sometimes even after it's been idling for an extended period) it's usually that first burst of combustion/accelerated combustion that has extra oil to burn off the top of the piston & when it does you get the by-product of that burn out of the tail-pipe.

[Tom]

You are just lucky. None of my trucks have ever puffed smoke.

[Gotenntitans]

Thanks guys.