1990 K-1500 350 chev oil consumption question

I have a 1990 Chev K1500 4x4 with a 350 in it with 138,000 miles. It goes through a quart of oil every 200 miles ( that's a LOT!). It's been that way
for a few years now. No oil leaks, no blue smoke except on engine start. It runs quite well, no plug fouling or missing. I figure it is either the valve oil seals, valve guides or both. Has anyone else had experience with this problem? Did you find a solution for it? Does anyone have enough experience with working on a 350 to suggest if the problem is usually the guides, valve oil seals or both? Is it practical to R and R the heads on an engine with 138K on it or is that asking for new problems? Any comments or suggestions much appreciated. Mike H. Seattle.
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Rings are shot.

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No, I doubt that the rings are shot, certainly no reason to be! If they were there would be blue smoke in the exhaust all the time. In talking to other mechanics, they seem pretty sure it is the oil seals or possibly the valve guides or both. I was hoping to find some one that has seen several of these with the heads off and was familiar with what is usually bad when looking at or rebuilding the heads. With the steep discounts that GM is currently offering, approx. 35% on a reg cab Z-71 Silverado, it may become more the problem of the local dealer than mine in the next couple weeks!!

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I'm not sure why you think the guides could be worn that bad, but the rings couldn't. In any case, a quart in 200 miles is a hell of a lot for just valve guides with no other drivability symptoms. Have you verified that your PCV system is functioning properly? If you pull the oil fill cap, do you get blow-by? H
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