[MagicRat]

Lots of carburetors have a momentary lean condition when you open the throttle, this is why the accelerator pump is there.
Often a lean condition can cause detonation or 'ping'. As you don't say if you get a hesitation when you step on it, so it can't be all that lean.
Hollys have an adjustable cam for the accelerator pump - there is a little plastic arm attached to the throttle shaft, it should be screwed into a hole on the throttle arm bracked labeled '1'. Try screwing the plastic cam into the adjacent hole labelled '2'.
This will give you a bit more gas through the accelerator pump.

Also there is an accelerator pump adjustment screw at the end of the arm. Turn the screw just enough to eliminate the free play in the arm (as measured just beneath the primary float bowl.