318 Engine stumble

The different cams (different colors) engage the pump arm at different amounts and at different times in the throttle movement; and you can flip the cam over and screw them in at the different holes in the cam to change the curve too. You can do a lot of customizing of the pump curve versus throttle position.

Here is a chart, which shows that the pink cam can have no pump shot just off-idle in certain positions, and can the slowest one to come in as you open the throttle when mounted in certain positions. IIRC the orange one is the typical one you get new but one position of the pink one is pretty close.
Holley accelerator pumps/cams | Grumpys Performance Garage

If there is a small gap between the pump arm and cam at idle position, that can be closed up and you should get a bit of dribble with any amount of throttle movement.