Quadrajets are notorious for leaking fuel from the primary wells. The problem is caused by the lead plugs that the factory put in to seal some holes that had to be drilled in the carb for fuel passages. Unfortunately, those lead plugs see manifold vacuum and leak a lot. It is rare that they will drain the float bowl, but your's may be doing so. After the car has been running and you're ready to park it, turn it off and remove the air cleaner. Then, look down into the carburetor while you run the linkage like you were stepping on the gas. As the carb opens you should see two streams of fuel squirting into the primary (front) side of the carb. That is the accelerator pump discharge and when it squirts, it tells you there is gas in the carb. The let it sit long enough that you know it won't start easily. Do the same thing. Look in the carb, cycle the linkage and look for the squirt. If no squirt, the float bowl is draining and the carb need to be repaired by someone who knows how to fix the bowl leakage problem. There is another possiblity and that is that your accelerator pump is worn out. If you don't get the two streams of fuel when it had just been running, the accelerator pump may be tired enough that it won't deliver enough fuel to start the cold engine. Also, if the accelerator pump is shot, you should be seeing a pretty good bog if you give it gas quickly. The accelerator pump is an easy fix, since a new one comes in every rebuild kit. The leaking wells are not.