But PJ, the accelerator pump and the power piston(power circuit) do not have the same function and the difference can be discerned.The acc pump only delivers a shot of fuel and an influence on the mixture strength momentarily when the throttle is MOVING toward increased opening.When that movement stops the delivery stops.
The power circuit adds fuel to the main jet delivery when manifold vacuum is lowered below a set point as in heavier load and increased throttle opening an continues to do so as long as the lowered vacuum condition exists.
So if the engine only stumbles when throttle opened but pulls good after the load/speed is increased look to the acc pump for weak or shortened delivery.
If, like on a gradually increasing grade with throttle being opened gradually, the mixture seems lean and the choke can help it but is needed continually the problem is probably found in the power circuit.
The Rochester is a sound and sufficient carburetor and will perform when it is right.
