car runs good for aprox 20miles then jerks and stops leave sitting for hour starts and runs good again?
It sounds like a heat related problem. Takes 20 miles to heat up, an hour to cool down. That could be vapor lock of the fuel in the engine compartment, maybe at the fuel pump. Spray water on it to cool down. Be sure to run fresh fuel blended for Summer usage. Also, the ignition condenser will heat up and short out on those older distributor ignition cars. You can run with a condenser disconnected as a quick test. Cheap to replace...they protect points from burning, better spark too. Maybe the coil is misbehaving too. I can't think of anything else heat related.
Is gas cap vent. Back in day took me months to figure out. Pop the gas cap open when starts to die and will start to run just fine again. Not hard to reach, right? And yes Wait a while and eould start up and run just fine.
Moss Motors has EVAP system parts for your car.
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