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Thread: too much fuel flow/pressure!

  1. #1
    Senior Member RACING JUNKIE
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    too much fuel flow/pressure!

    set up: Edelbrock 4 to 9psi fuel pump, all 8an steel braid, sumped tank w/ Mallory filter, Holley bypass reg w/ 6 an back to tank. QF 950 HP carb (new) & I have 2 fuel guages (one liquid, one not) I run 6.5psi currently & on the street. Problem started after installing regulator/bypass back to tank & new carb. Car is mostly a street car now... was a drag car. (BBC 69 Camaro)

    Problem: when cracking the float bowl nut & setting floats, excesive pressurized fuel comes out. Float nut is on top of carb, not on side like my old Holley DP... There is no way to set floats w/o alot of fuel comming out of carb... I was told it "should just trickle out" when floats are set right... I can't get a "trickle"... It comes out too much no matter what. Everthing is new except tank, fuel pump & the 8 an from tank to pump. No leaks... The hose from regulator to carb is 6 an. The bypass return is all 6an (new). Rest is all 8an. Why can't I get the flow of fuel down out of float adjustment nut??? Car seems to run pretty good ironically... no ring wash yet or fuel in oil. Any help is appreciated. God Bless-

  2. #2
    Senior Member EXPERT BUILDER
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    did you try to addjust your floods al the way down so nothing comes out,then back up.i,m not sure of the setup your talking about on your carb so someone might know better.good luck

  3. #3
    Senior Member RACING JUNKIE
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    John858: Thanks. Seems like I have, but I can't remember if I adjusted the floats alll the way down... I just know I have lowered/raised them multipe times. & I think I am getting fuel back pressure somehow.I am going to look at the tank/ return outlet too. Thanks for the reply!!

  4. #4
    Member JUNIOR BUILDER
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    One thing that I see with your combo is that your using an -8 line for a feed and a -6 line for a return. They should be the same meaning a -08 for feed and return or -06 for a feed and return. I have seen guys use a -6 for a feed and an -8 for a return but never have I seen anyone use a bigger feed- small return with any success.

  5. #5
    Senior Member RACING JUNKIE
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    Thanks- I thought about that... it's one of those things you really don't want to hear after spending the money & doing the job... I hope that it is not the cause, but it sounds like it could be. It is 8an from tank to carb, & 6an from reg return to tank. I have heard people say not to go up (like from 6an to 8an). I figured that the return line would not matter as much.

  6. #6
    Senior Member RACING JUNKIE
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    If the floats are holding their set, and you don't have fuel running out of the boosters, don't worry about it. Set the floats to the right height and go have fun.
    -WJ Birmingham

    OneBadGMC.com

  7. #7
    Senior Member RACING JUNKIE
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    The nut on top raises and lowers the needle and seat..the screw /plug in the side is the sight plug so you can check the level...if there isn't one I would bet the farm there is a sight glass there instead...that is where you want it to just trickle out. The one on top should have a lock screw on top of it...break it loose while holding the hex with a 5/8 wrench...when you turn the nut up and down the float level will go up and down. It is normal for it to have preasure there..mine always has squirted a bit when I loosen it. One way to get a holly style float extremely close without it running is to turn the bowl upside down and adjust the needle/ seat until the center of the float is about half way up the sight plug/hole. This will be really close when you start it up.

  8. #8
    Senior Member RACING JUNKIE
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    Tod74- you are absolutely right!! this has made the most sense so far. It is a QF950 hp which replaced the 850 Holley dp... the QF has sight holes where the Holley had the float bowl nuts (which is what I am used to). The floats are holding, & I use the sight windows now to adj the needle & seat level... I was thinking that the "trickle" of fuel needed to be the same either way... not necessarily the case. I have no ring wash... or smell of fuel in oil... so it's good. THANK YOU!! Carbs to me are like Calculous... we avoid each other with denial.


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