Howdy Back Kevin:
It sounds like you're still chasing the source of your stumble problem.
More specific information would be helpful. What vehicle? what engine? What trans? Is this carb original/stock/OEM?
If you have a Holley, that is stock and original, you either have one of the side hung float bowl carbs used from 1960-62, or a 1980-82 vehicle with the #1946. You may have a Holley #1940 which is a replacement carb. But, I'm only guessing.
The early glass bowled Holleys have a series of holes on a lever to adjust the accelerator pump. The #1946 carbs use two bent rods (not easy).
Know that an off idle stumble can be caused by not enough initial advance. About 50% of carb problems are really ignition problems. Another 50% can be traced to a vacuum leak(s) problem. That leaves at least, another 50% to dirty, worn, poorly tuned carbs. And that leave % lots of room for other possibilities.
Before I'd change the accelerator pump timing, I'd make sure there are no vacuum leaks, ignition is in tip-top shape and functioning properly, and that the accelerator pump is squirting a nice stream of gas when the accelerator pedal is depressed.
Your fuel pump should have a one way valve in it to keep fuel from draining back to the tank. It may or may not be working. If not working, it will take just a little more cranking time, or the engine may start and then die, but start easily again. It is not a big problem.
Adios, David
