View Full Version : Carb fuel system help

03-14-2005, 10:51 PM
I would like to sump the fuel tank and add an external electric fuel pump in my 72 Chevelle but need help with other issues such as:

Is a return style regulator and return line necessary/recommended?

How should I vent the tank if I have removed the vapor canister?

Is more than one bung required if I do not run a return line?

350 cu in / 350 hp / Demon Carb / blue holley fuel pump+regulator

03-15-2005, 06:18 PM
with only 350 horse you won't need too much of a fuel system, in fact a decent mechanical pump would really be fine, a sumped tank and electric pump and return etc or going to be overkill. if you plan on a bigger motor later there is nothing wrong wtih overkill, unless you might go fuel injected in which you would have to change over the system. But if you want to know here is some info
with a basic pump like the holley color series, a return is not necessary, the pump will internally bypass. In general a fuel system that uses a good pump and a return is a better system than a non return system. The pump will last longer and will be quieter, and the fuel will stay cooler. There is a way to modify a dead head regulator(what you have) to make it a return style but you will have to research that yourself, i am not sure where that info is. The return line should at least be the same size as the supply line. So a return is better but not always necessary. If you remove the charcaol canister you need to vent the tank, either by a venting cap, or some kind of external vent. how to do it, I am still trying to figure out. One bung is fine because you can always run the return to the top of the tank where the pickup used to be. THat is how i do mine, so the returning fuel doesnt have to fight its way into the tank, it just drops down.
BTW the holley blue pumps have a reputation to be crappy and break all the time. I would consider a mallory pump

03-15-2005, 10:21 PM
Im all about saving some money...so what about the sump to still protect against the pickup being uncovered and a mechanical fuel pumpfor if/when I get the cash to upgrade my powerplant?

The sump will be in place for an electric fuel pump as well since the tank is out to do the work now.