98 Buick 3800 Smokes BAD!

This is NOT the Upper intake manifold (UIM) coolant near the EGR pipe issue, although the story starts there. My neighbor's car used coolant and died. i bought it as I am getting pretty good at head gasket and upper end repair. I replaced the UIM because it had the classic problem of the plastic eroding around the EGR pipe and allowing coolant that circulates in that area to leak into intake. the whole upper end was coated in dark gooey crap. The cylinders were leaking bad. I pulled the heads, cleaned them and the lower intake manifold. reassembled all parts and started it up. It had a misfire that came and went. i drove about 25 miles with no problems other than misfire. The next day, I started it and was trying to find cause of misfire when the entire neighbor hood filled with thick smoke. it is blueish and smells like oil. I can start engine and run for abou t4 minutes with NO smoke, then thicker than anyting I have every seen. I have replaced the PCV valve and added rislone to the oil. no change. I read one advice column saying check the drain back holes in head. I'll be checking that tonight or tomorrow. as well as looking to see if the smoke comes out the oil fill cap. I can also do a leak down and compression tests. What else should I look at? I want to determine if the rings are the cause before doing a teardown or replacing the engine.

Make sure both o rings are under the map sensor for the pcv valve.

Thanks. The pcv valve o-ring wasn't in place. There was a lot of oil in the manifold. it took a while to clean out all the oil. By then, plenty oil was in the exhaust.
I removed and cleaned the Catalytic converter (which was just replaced because the coolant problem + 149k miles had it VERY plugged up so it had no power.)

It still blew smoke and misfired. There was no smoke coming out of the oil fill nor the PCV - checked with the MAP cap off - so I hit the road. At first it was slightly better. I drove about 5 miles and no further improvement. then it got better. much better. No more smoke, only an occasional misfire.

You may have to change the plugs, if they were oil soaked to eliminate misfire.