The easy test is take the inlet to the carb off and connect a rubber hose long enough to reach a safe place outside the engine compartment, then put the hose in a coffee can and have someone start the engine. You should have a steady forceful stream into the can (at least a pint) . If it starts out good then falls off in less than 30 sec, then check the sock in the tank for being restricted. These are old cars. Just had a old chev with a plugged sock and it would run but not very well under load, changed the fuel pickup tube and pump and now runs 4-0.
Oh, just to make sure you know, fuel is flammable, be careful when spraying it around a hot engine :-)
Last edited by Bob Young; 06-05-2018 at 09:47 AM.