Smokes upon start-up ?
 

My '94 K1500 5.7/4L60E blows smoke for almost a minute when I first start it and then runs fine with no excess smoke. I'm guessing the computer takes that long to adjust something. I've put new plugs, O2 sensor and cooling sensor in it. What else should I check ?

Re: Smokes upon start-up ?
 

Might be valve seals are worn, allowing a small amount of oil to seap into the cylinders when after you shut it down.

Re: Smokes upon start-up ?
 

What color smoke? Mine puffs a cloud of blue smoke, but that's just from bad valve stem o-rings. Got em, but just haven't changed them. If your's does it that long, it sounds fuel related. Does it smell rich? Does it do this when hot or cold? Both?

Re: Smokes upon start-up ?
 

Valve guide seals typical problem w chevy

Add some marval mystery oil to crankcase n ill put money on it getting better shortley (my 90 smokes very little now)
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Re: Smokes upon start-up ?
 

I think you're probably right about the valve guides, since it has almost 150,000 miles. I'll try some Marvel to get me by until the rebuild/replacement. Thanks !

Re: Smokes upon start-up ?
 

+1 for valve guides. Mine does the same thing, after startup and even after I sit and idle at a stoplight. Changed the valve guide seals a couple years ago, but that didn't cure it; I think the guides themselves are just that worn. 190k on stock heads.

Re: Smokes upon start-up ?
 

I added a bottle of Bardahl No Smoke and it's smoking much less. I guess it'll get me by until I rebuild the junkyard 1998 5.7 Vortec motor I plan to drop in someday. Thanks guys!