Quote:

I think older holleys used a ball with a cylindrical weight stacked on top.



Yes they did you are correct. That is the acc pump discharge check valve or ball as they call it. It lifts up when fuell is pushed up to it by the acc pump when you step on the gas. But it needs to seat when off the gas as the pump draws fuel back into its plunger circuit and it it dont seat it can draw air in also and cause a stumble. And as said it can cause fuel to siphon out. Ron