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Electric Fuel Pump Max Acceptable Pressure

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  • Fuel System: Electric Fuel Pump Max Acceptable Pressure

    What is the max acceptable pressure at the carb inlet?

    I have read that the 8psi output of a typical pump is too much and will flood the carb. I see that "low pressure" electric pumps are now available that only produce 4psi. Is this low enough to work with our carbs and not cause a problem? I have a WCFB on my Hawk and a Stromburg on my 54 Commander. I currently have a Holley regulator on my Hawk and the pressure at the carb is only about 2.5 - 3.0psi.
    "Trying to shed my CASO ways"


  • #2
    2.5-3 pounds. I have an Edelbrock 1403, and I had to install a regulator on my Carter electric pump. New carb, float properly adjusted, but the pump over powered it...
    Last edited by 345 DeSoto; 08-29-2018, 05:24 AM.


    • #3
      I have a "Cube" type fuel pump on my Studebaker (350 Chevy/Edelbrock carb.) that is rate at 4 pounds. It also feeds to the stock mechanical fuel pump. While primarily for priming it seems to deliver all the fuel necessary without a regulator (though I think the mechanical pump may be taking care of regulating pressure). On my Valiant (also Edelbrock carb.) I have a 4-7 PSI "Cube" style pump. Because of prior issues with the stock mechanical pump I do have a regulator and if I recall correctly set to about 4 PSI. In this case I have bypassed the mechanical pump. In both cases "Cube" pump works well. So, 4-ish PSI seems close.

      One thing I have noticed about the Ebay (Chinese) "Cube" pumps is if they are rated at 4 PSI or lower the GPH is higher (90) and if rated at 4-7 PSI the GPH is lower (70).. so, they may both be the same save for a restrictor that increases the pressure at the sacrifice of volume.

      If used only for priming the PSI probably doesn't matter - much. Given these "Cube" pumps cost about $15 shipped it is actually cheaper to buy both pressure types (low/high) than to have to $pend $30+ for a regulator (Holley) if the pressure is too high.
      '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


      • #4
        The lowest pressure that meets the needs of your engine and the way you drive is what you should shoot for. For most street cars 4 psi is plenty, but often less is required. I had a car with 3 carbs with a regulator set at 1 psi and it worked fine at full throttle, over 3 miles at least.


        • #5
          I agree with bensherb. I regulate my Holley rotary pump with a resistor to lower the voltage, so I get 1 to 1 1/2 PSI on my 50 Champion, and it works fine at all speeds.