Originally Posted by oldbogie
This probably shows the mixture drops lean when the throttle is opened, this is common with a big cam as the air flow dies momentarily and fuel falls out of suspension. With no continuance of detonation once mixture velocity picks up, I'd say you need more accelerating shot and maybe the power valve needs to come in sooner (i.e. a higher vacuum).
You will, also, have to figure out if the secondary opening drops the mixture lean as well; although vacuum secondaries tend to be more graceful than mechanical in this regard, it still could be a problem. The Q-jet suffered in some applications with this to where they put enrichment ports just above the closed air valve so when it would start to open it would pull some extra fuel. Holley, of course, has the "famous" double pumper for the same reason. You could either add this feature if it isn't on the carb, or increase the secondary metering a couple jet sizes, or put in a stiffer spring to slow the secondary actuation a bit.
I just thought of something. My carburetor occasionally feels like it's getting air in the accelerator circuit at idle. It will hesitate, BUT if I give it a few revs in neutral, it kind of gets the air out, then I have a nice clean rev from there after. I've already replaced the acc pump diaphram, tightened down squirter nozzle, replace metering plate gasket. It usually only does it when the engine is cold and clears up after a while of driving. Think this could be related?