stock 348 dies after running for ~1/2 hour

[409Kid]

Have you ever cleaned the fuel tank. It’s very possible there is enough crap in the bottom of the tank that when it gets agitated enough it eventually clings to and occluded the strainer. When you shut the car off the crap falls back to the bottom of the tank until you take the car out again.

 

[Dean's 61 bubble]

POSSIBLY.....think about it....ethanol fuel (propagated on us by the feds) is not only very corrosive, but has a VERY short life span....probably more on the line of 6 weeks to 2 months (NOT 6 months) Alcohol free gas could last considerably longer and can be found at many stations. Anyway, not wanting to pull the gas tank, is understandable, but usually is where the problem is...but if you are running a carb the ethanol will evaporate at a rate great enough to dry the float bowl in a month or less and corroding the metal as it does, junking up the carb. Oh, when you do pull the tank, don't be surprised when you shine a light into it. Also, i wouldn't try to clean and "reline", unless new ones are not available. If you are NOT fuel injected, by all means find a station with ALCOHOL FREE gas, either regular or hi test depending on your needs...your car will thank you for it. Just my opinion guys

 

[Lt.FrankDrebin]

I usually use ethanol-free fuel, unless I have no choice. But anyway, the problem seems to be in the fuel pump. I already determined that when the car dies, the fuel pump isn't pushing fuel, nor is it pulling fuel. I detached both of the lines at two different instances. One of the instances - no fuel being delivered to the carbs. The next instance - no fuel being pulled; not even out of a can right next to the car. Well, today I pulled off the fuel pump - yet again. Where does the actual pumping occur in this pump, in terms of travel of the lever? It seems that most of the lever travel does nothing.

 

[La Hot Rods]

If most of it feel soft it is probably bad.

 

[DaveN]

easy to rebuild an original pump with newer ethanol resistant components I've rebuilt several pumps and they are still going strong (knock on wood). Also check that fuel filter if its partially clogged the pump will not push in enough fuel to keep your engine running after a period of time.

 

[32witha409]

When the lever is pushed is draws/sucks the fuel, when it is released the spring applies the out flow pressure. Here is a basic pump cutaway.
Place the pump rod between the eccentric and the pump lever.

 

[32witha409]

I can't come up with a reason that a pump would pump then stop pumping over and over again. A long shot would be that you are some how creating a large vacuum in the crank case that is 6 ponds or more. Doubt that is possible.

Put a pressure gauge on the pump outlet and see what it does. Once started the pump should pressurize and stabilize with only a slight pulsing. If the pressure continues to pulse violently the pump is marginal and bad.

 

[blkblk63ss]

Put a return line kit back to tank since you have dual carbs sounds like vapor locking .