loser.. the carter afb, like all 4 barrels, dumps fuel into the primaries. I know of no double pumper 4 barrel that is a vacumn secondary. double pumpers (primary and secondary) are mechanical secondary carbs .
If the fuel filter is clogged it will run the bowl out of fuel.. the car will die but.. the fuel filter may then allow enough fuel to get in during coast down (stick) or cranking to start the car. there may be enough fuel getting in to run for some time but not enough to keep up with engine demand.
This is a "paritialy clogged" filter.. it should really show up if you left the car in a low gear and just ran at high speed (increasing fuel demand) the carb bowl would run out of fuel that much faster. The car really should act like it is running out of gas tho (sputter and catch).
It also could obviously be an overheating coil... this is rare but possible. If you have a spare that you know is good... change em out.
lazs