Whoever rebuilt that carb botched the job! No excuse for not wet testing the accelerator pump system after performing a rebuild!
I test all my builds using clean solvent in a recirculating tank with a hose/filter to connect the nozzle with the carb fuel inlet using a fitting adapter if need be. That fills the fuel bowl(s) completely allowing verification that the needle/seat(s) seal properly and then loads the accelerator pump well so that you can wing the throttle lever and watch the squirt stream and pattern. Many carbs have an adjustable pattern that can be fine-tuned during assembly both for direction of squirt and for volume. And the carb must be held in it's normally operating orientation when doing this so that solvent does not "slosh" out the vents and down the venturis which will give a false indication.
In the case of your quadrajet, the fuel bowls must be solvent-filled and then the carb elevated and allowed to sit for at least thirty minutes while ya watch for drool out of the plugged passages in the bottom of the bowl segment. If it leaks, then it must be repaired, otherwise raw fuel will continuously drool down the intake plenum, a condition you cannot tune out. And...in a hot-soak, raw fuel will pour down the gullet so that when ya go to re-start the motor it will be severely flooded due to percolation and leaking quadrajet passages!
The quadrajets were awful when new for allowing raw fuel leakage, and their competitor carter thermoquads had the same situation occur but due to a somewhat different reason. All of the so-called" superior" design features of both of these carb series was negated by their extremely bad habits when placed in service. And the aftermarket made big bucks in coming up with "fixes" for both carb series.
