That eliminates a few things. Like Rick said, there's a vent in the top of the vacuum tank that could be clogged. Did you just buy the car, could it have been sitting, how about a wasp clogging up the vent? WHile you are waiting for it to restart can you hear the carb gurgle like gas is running into it? Next time it quits can you open the drain on the carb and see if there's gas in it?? My first thought was ignition, have you done anything there? A bad condensor will run for a while, heat up and short out, then when cool will restart. These things are fun!! I wasted lots of time chaseing a backfireing problem that turned out to be a carbon track around the distributor cap. The car ran good for anywhere from 30 seconds to 15 minutes, then crossfired and belched black smoke. I'm sure there will be other suggestions too. Be very methodical and make sure you try one thing at a time. Even that way it may correct this problem but start another.