Interesting Weber jetting

[Gaz64]

I'll add a little more.

At ANY throttle opening (steady throttle), the inlet valve is open. The ball to be has forced up on it's seat from fuel pressure within the pump cavity.

The compressed piston spring determines pump pressure. Pump rod length, pump jets and bypass orifice size determine duration of shot.

The inlet valve can have no bypass 00, or 0.35, 0.50, 0.60 etc.

The inlet valve can also have a steel or plastic inlet ball. The plastic ball seats faster because it is lighter.

All other circuits of the carb should be optimised on their own with no input from the pump circuit. Then and only then should the acceleration circuit be addressed.

As can be seen on Eljaro's car as example, the pump circuit can be backed off, there is seldom need for a closed bypass.