Hey Chris, is the bottle that you dump the breather hose into open on the top so it can vent? I am sure you know this since you have been around for a while, but it doesn't hurt to ask
Could it be possible that a valve seal fell off when you were changing cams? You didn't take the retainers off at all, did you? Who machined the head? Sounds like it maybe be a bad machine job if it was rebuilt recently.
Threaded Mode