<VV> no throttle response after stopping

[Grant Young]

<<It's been about four months since I did a major carb cleaning & rebuild>on my '63 Monza, and in recent weeks I've begun to experience a behavior that's bound to be carb-related. Very rarely (like once a week) I'll be stopped at a traffic light, and when the light changes, I get no throttle response whatsoever until I pump the accelerator a few times.>>

Since the problem started after a rebuild, there is probably something related to that. My guesses are: that the float level might now be too low and there is not always enough fuel in the pump cavity for a good pump squirt. BUT, you should get a delayed response even if there was no fuel in the cavity. It would be a "bog", but the carb would work (poorly) even if you remove the pump cup. You can easily check you pump response by looking into the top of the carb (engine off) while operating the accelerator shaft. It could also be that something like a slab or piece of varnish loose in a bowl and is settling over the main jet when you stop for a while at a light. The needle could be getting cocked in the seat and not working properly. I don't think it is loading up, because the usual result of that is that the engine dies (floods) when you try to accelerate. Pumping it and getting it to run would instead indicate a lean condition, so you might try turning the mixture needles out half a turn at a time to see if it improves.  Hope this helps,
Grant