Well, where can the oil come from?

The oil pasages, from the rings, or from a defect in the block or heads...anywhere else?


With a global problem like you seem to have, I'd suspect a global cause- something common to all of those things

I'm not familiar with the 351W at all, and I don't know the oiling system at all...but you mention some head problems. Does the 351W oil anything through the heads?

With exhaust valves recessed and a valve stuck, is it possible that your valve seals let go all around? or that they were damaged during installation? Just guessing

It might help to know more about the engine itself, and what if anything, has been done to it prior to your problems