In 90 degree heat, after an hour in stop and go traffic, the 355 SBC in my 29 Model A began loading up when stopped at traffic lights, stalling when starting to move, then ultimately shutting off completely. For intake, the engine runs two Holley 600 carbs, a Holley electric pump, and a Weiand/Holley 250 blower. When I restarted the engine 15 minutes later, it belched blue smoke, evidencing flooding. Fuel pressure never went about 5.5 pounds and I had only been ightly feathering the throttle. We discovered the cause of the flooding after first removing the air cleaner on the carb closest to the firewall. While my friend Steve cranked the starter, I, being careful to look at an angle so as not to get burned by a possible backfire, watched fuel flow into the carb. Fuel was gushing, not just dripping, into the rear carb from the gas tank vent. The vent is plumbed from the tank to route any overflow back into the engine, and not dangerously onto the exhaust or electricals near the gas tanks. There are two tanks, joined by a crossover tube, installed alongside of, but shielded from, drive shaft and each tank has a vent. The current vents are, however, located at the front of each of the two tanks and, since the A has about a 6 inch rake, the vents are not at the highest possible point. We plan to install vents at the rear of the tanks, and at the highest point. Any thoughts or suggestions are welcome. Thanks.