Blue smoke after engine runs for a few minutes

First a little background information. 91 OCC, 211,xxx miles on it. When I bought it I realized that it needed valve stem seals. Typical blue smoke when leaving a stop light then it would clear out. Purchased it 250 miles from my home and it did this the entire trip. Since then I have replaced all the valve stem seals. While doing those we noticed that the oil drain holes in the head were clogged so I tried to clear them with a screwdriver. The seal job was done about 40 miles from my house. Drove home with no smoke. Let the car sit for about 10 days and when I went to start it and let it run while checking other things it starting smoking and no amount of revving the engine would blow it out. The neighborhood looked like a fog bank had rolled through. I then ran Amsoil engine flush through per the instructions and changed the oil. Inside of engine is cleaner but same result when car is started. Pulled the oil fill cap to check for excessive vacuum or pressure thinking it may be a PCV issue and noticed the oil was covering the valve spring. So I pulled the covers again and used bore cleaning brushes to really scrub the drain back holes. Pushed them down at least 3 to 4 inches. Put it back together and same result. Crank it up no smoke. Let it run for about 5 minutes and blue smoke for miles. I have not driven it while it has been doing this because I also am having a fuel pump issue that I have not addressed yet and don't want to get stuck on the side of the highway again. So any ideas on any other avenues I should explore before I pull the engine? I'm leaning towards rings but I am no expert so any advice and shared knowledge would be greatly appreciated. I am ready to drive this thing without fear of shutting off OR people thinking mosquito patrol has a new old vehicle.

It could be the valve guides. I just bought a 92 OCC that had that problem. The previous owner had the heads rebuilt, and it no longer smokes.

I had the same problem, the engine in my 91 OCC had had 8 oil changes in 23 years. The motor was just clapped out.

I fixed it by replacing the engine with a new goodwrench unit. Has been mostly fine ever since.

You could always put a crate 454, or a 502 in it with a built 4L60 (not E) trans.

another area to check before condemning the engine is the PCV circuit. On the throttle body cars, the PCV circuit inside the TB tends to coke up. In my case (same symptoms) the PCV valve was functioning but so little flow through the TB was pressurizing the crankcase. Removed the TB and removed the coke buildup inside the PCV circuit and that corrected the oil burn.

Note: Removing the TB and doing this on the bench is the only way to get at this circuit from both sides.

Hope this helps.

Bill

You should do a dry/wet compression test to eliminate piston rings as a possible cause. Good luck.

I saw this once on a GM pickup of that vintage. After changing valve seals it still blew blue smoke when warmed up. It turned out there was so much oil coating the inside of the exhaust system that it would re-vapourize as the exhaust heated up. It took days to clean out the oil film.