Hi I just installed new valve covers on my 351. After I started up the engine it starts to smoke closer to the back. I think the only thing that would cause it, is pieces of old cork gaskets got into the oil after scraping them off. It smells alot like something is burning and looks like it is coming up from the transmission area or close to where the headers flanges meet the exhaust. if anyone knows what would cause it. the smoke is white if that can help identify it.
In most cases when the valve covers are removed, some oil runs out and gets on the exhaust. It takes a little running to burn it off. If you just finished and were warming it up, I'd say to run it a little longer and keep watching to make sure that it doesn't get a lot worse. If it just stays the same, it'll probably quit. Try blowing it in that area with the blower from a vacuum cleaner if you don't have an air from an air compressor.