[Argess]

It does sound like an acclerator pump issue. Either too much, or not enough. For a start, assume it's not enough.

I assume this is a Holley?

Since it's such a short delay, cheapest easiest way I'd start with, is to change accelerator pump cams. If you don't have a kit, see what happens by moving the cam screw to #2 hole vs #1

Advancing your intial timing can help a lot as well. I"m running 20Deg intial and 38 max, whihc is not unusual for these cars.

Finally, I have been advised, though can't say I tried it, but sometimes the carb woks better with the idle mixture screw set for a slightly rich mixture, maybe up to 1/4 tunr further out