BW,
It has been a while since I worked on a 216 intake but my dim recollection is that it is similar to a 235/261.
Is there a chance you have the carb gasket and/or insulator on wrong? There is a notch/hole in the gasket and a notch in the insulator (between the carb and the intake) that is a vacuum "journal" (at least that's the case on a 235/261.
Maybe someone with more experience will reply.
Good luck,
Tim
