JDR Performance wrote: ↑Fri Nov 03, 2017 2:42 pm The engine wouldn't run without vacuum below the carb. I would put a spacer with a vacuum port between the carb and manifold to check how much you have and look closely at the bottom of your carb and mounting gasket to see why it isn't seeing it at the port.
That's what I think. It can't run without a pressure drop.
I also looked closely at the gasket and the ports on the base of the carb. I wish I could post pictures. It's just a #54 Mr. Gasket open 4150 gasket.
I'm going to try Mark's idea to blow a bit of air back into the PCV valve port and see what happens.