Thanks Manim not an F guy. but its common to goof the headgaskets on some
of those motors. sometimes you have to flip one over when you
install it. my brother once bought a F motor aftermarket that
had the headgasket on backwards. it smoked and overheated.
my thing is you said its been rebuilt. but any guy thats rebuilt
more than one should already know to flip the gasket over
idk man,hard to tell really how deep the stink hole goes
gl with it hope it works out for ya