When I rebuilt my carbs last year, the Holley tech told me to use the blue bowl gasket, as the primary reason for vacuum secondary problems is that the older gaskets will fail and allow the vacuum chamber to fill with gas. No vacuum chamber, no vacuum. The gasket was $7 apiece, and I have no alterations on my setup at all. I completely rebuilt everything on all 3 carbs, and it all works flawlessly. When I take off in first gear and nail it, it’s like 2 different motors coming together. The rise is rpm is very noticeable, and the car actually gets a little squirrelly, and the power is 2nd to none.
I rebuilt the vacuum pods in the 2 outboard carbs as well, so maybe a complete rebuild of all components is in your future.
