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Thread: FUEL PSI AND LINE SIZE

  1. #1
    Senior Member DYNO OPERATOR
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    FUEL PSI AND LINE SIZE

    I HAVE HOLLEY BLUE ELECTRIC FUEL PUMP AND THERE REGULATOR WHILE MY ENGINE IS RUNNING THE GAUGE REDS 6 TO 6.5 PSI I ADJUSTED IT TO 7 AND A BIT LATER IT FALL'S BACK TO 6 IS SOMETHING WRONG?I HAVE 8 AN FUEL LINE FROM THE TANK TO THE CARB IS THAT OK OR SHOULD I BE USEING SMALLER LINE FROM THE REGULATOR TO THE CARB?

  2. #2
    Senior Member RACING JUNKIE
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    Re: FUEL PSI AND LINE SIZE

    Quote Originally Posted by JEFF69Z28
    I HAVE HOLLEY BLUE ELECTRIC FUEL PUMP AND THERE REGULATOR WHILE MY ENGINE IS RUNNING THE GAUGE REDS 6 TO 6.5 PSI I ADJUSTED IT TO 7 AND A BIT LATER IT FALL'S BACK TO 6 IS SOMETHING WRONG?I HAVE 8 AN FUEL LINE FROM THE TANK TO THE CARB IS THAT OK OR SHOULD I BE USEING SMALLER LINE FROM THE REGULATOR TO THE CARB?
    8an is fine, when it falls back to 6, is this after the car has been running for awhile ? if the gauge is close to the heat and is liquid filled it will vary
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
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    APD Race Engines
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  3. #3
    Senior Member DYNO OPERATOR
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    Hello Holly blue

    Also in addition to the heat issue possibility, this is the reason that regulators are so expensive that work well, meaning repeating there set pressures. The fuel pump has a pressure regulating spring in it and could also be causing your fluctuation in pressure. The holley blue comes with a regulator thrown in the deal when you buy them from some sources, this may give you some idea of it's relative value and reliability. That pump will not ever out run your #8 line. More expensive pumps have closer machine clearances and perform more smoothly and reliably as far as pressure consistency is concerned. Running less than 7 psi is recommended in most all gasoline applications. If the pressure drops more than 1.5 PSI from your set pressure the fuel level in the bowl will fluctuate too much give constant fuel ratios and needs to be corrected. Your complaint is not new or unique, but if you minimize the pressure fluctuations your car will perform more consistently and probably last longer too.
    Bruce

  4. #4
    Senior Member DYNO OPERATOR
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    it falls back after running awhile and then i cant get it back to 7 psi.the gauge is liquid filled and a jegs brand and is about 2-3 inches from the intake.i guess i shouldnt have the regulator mounted on a bracket i made bolted to the head.

  5. #5
    Senior Member RACING JUNKIE
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    The Holley blue doesn't have a return, therefore it will loadup and has trouble getting going again when you need it. I wouldn't run a Holley blue in a rear tank application. Money well spent to get a Magna fuel pump with return and a Magna fuel regulator. You problems will go away. JMO

  6. #6
    Junior Member JOURNEYMAN
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    Quote Originally Posted by dparker
    The Holley blue doesn't have a return, therefore it will loadup and has trouble getting going again when you need it. I wouldn't run a Holley blue in a rear tank application. Money well spent to get a Magna fuel pump with return and a Magna fuel regulator. You problems will go away. JMO
    X2 on the magna fuel, l ran holley blue pumps until l had every hair yanked out of my head then put a pro500 magna fuel with a fuel log and dual reg's one for carb other for nos and never ever had another issue

  7. #7
    Senior Member MASTER BUILDER
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    I have a Jegs liquid filled fuel pressure gauge mounted under the hood and when it gets hot the gauge shows a lower pressure,sometimes real low depending on how much heat.Anyway i borrowed a non liquid filled Stewart Warner pressure gauge and set my fuel pressure off of that and really don't even worry with mine anymore.Something for you to check out,take some ice in a bag and put it on your pressure gauge and let it cool for a little bit and watch the gauge change.


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