Details...Details....Is the motor stock, whats the condition of the shortblock, milage, etc. anything that could pertain to this problem. Off hand without knowing all that, I would say you have excessive blow by or you may need to change the pcv valve.
Its cheap, you might as well replace it. Sometimes the PCV doesnt open (either all the way or not at all) which is how the crankcase is evacuated, along t=with the hose from the v/c to intake.