Intake manifold Not seating properly (?)

The pcv valve itself was rarely the location of fault. Most cases the port ( metal tube ) at the carb was totally clogged. I've found the rubber hose connecting the two filled solid a few times also.
I'll place the intake clean and dry and use a sharpie to mark where the RTV bead belongs. Clean and dry is very important. Allow 24 hours for RTV to cure is just as important. A heavy bead of the stuff aint going to cure in a minute like whats on your fingers. I said that because surface finish matters. Ever notice how a thin coat of RTV will slide off a putty knife blade a lot easier than off your fingers. Your finger print ( surface finish ) is the difference.
Here's a good example. Take a very close look at the factories finish on OEM heads and you'll see tool marks )))))) left by their shell mill. Same finish appears on the block rails, OEM intakes, etc.. Sure they could have produced a mirror like finishes. That's not what engineering called for. If you were to magnify the surface you would see peeks and valleys like vvvvvv. There is what's called R.M.S. spec on engineered drawings ( details on that get too technical ). My point is, Getting the valleys clean and dry isn't easy but they do need to be there and they do need to be clean and dry.