My motor is smoking!

Back when I was a kid I had a 70 Chevelle and it burned oil bad. I ran it that way for a month before I bought a good used 350 from a buddy and put it in. The exhaust system was so full of oil build up that at first I thought there was something wrong with the new 350 because it smoked as bad as the old engine. Took several days of driving to burn out all the oil residue. Finally went away after about a week.

Hope this is your case too but like you said doing a valve job on worn rings can cause this also. I'd say give it a week to 10 days to burn out any residue and if it's still smoking you know it's the rings.