More speculating, but if you happen to have this style spacer under your carb, be aware you must use an application specific gasket between the manifold and spacer. A generic parts store 2-barrel Holley/Autolite/Motorcraft pattern gasket used here will cause a vacuum leak.
That's the spacer I've used for many years with any of my carbs including the last Holley carb and also including an old 2V Autolite before the current Holley and had zero problems. Using, if my memory serves me correct, was either a Holley or a felpro gasket bought at a chain auto parts store.
The current Holley is the one I'm having trouble with with what appears to be a vacuum leak.
cj750, let me in on what gasket you would recommend between the manifold and the spacer AND the gasket between the carb and the spacer.
Is the spacer you show the one with the bottom that is hollow like, sort of 2-3 cavities with very small gaps between each cavity?
Guys, thanks for all the input, I really appreciate it.
Rich