Suburban burns oil. Rings or valves?
My 1994 burns oil and fouls plugs. There's 204k on the clock but the real mileage is anyone's guess. I got it for cheap because the PO overheated it and cracked both heads. I bought a pair of used junkyard heads and all I did to them was put new seals on. I freshened up the bottom end, put in new rings (cylinders were pretty clean), bearings, timing chain and oil pump but otherwise it's still pretty much stock.
The thing is I know it's burning oil, around a quart every 1000-1500 miles. It runs pretty well but when I idle for any length of time, like at a long traffic light, it runs pretty rough for the first 10-15 seconds of acceleration. After that, it runs as smooth as you would expect a 20 year old, 200k plus mile engine is going to run.
My guess is the valve guides/stems are worn and it's pulling oil past at high vacuum. Is there a way to check this theory? Any other suggestions?