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Holley pump nozzle tuning

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  • Holley pump nozzle tuning

    Just a quick question. How big of an effect does squirter size have on afr? I know it efects transfer fuel but i went from a 28 squirter (idled at 13-13.5:1), changed to a 25 and the whole thing leaned up, idles at 16-17:1 now‍♂️ no ther changes at all.
    Only thing i can think is the others are pulling fuel at idle?? Idk, crazy
    Last edited by Lit549; October 26, 2021, 11:36 AM.

  • #2
    I am guessing you answered your own question since nobody is replying, but since I still want to learn about carburetors I know a few things happen. I know if you do not have a gap on your pump level your squirter will dribble fuel at idle to the point that vacuum will suck the fuel from it constantly. It should not be doing anything until acceleration.
    Jets, air bleeds mixture screws sounds like they would need to be richer, but check to make sure you have a gap first. Even increasing your idle speed gets your pump lever closer to contact.

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    • #3
      Originally posted by anotheridiot View Post
      I am guessing you answered your own question since nobody is replying, but since I still want to learn about carburetors I know a few things happen. I know if you do not have a gap on your pump level your squirter will dribble fuel at idle to the point that vacuum will suck the fuel from it constantly. It should not be doing anything until acceleration.
      Jets, air bleeds mixture screws sounds like they would need to be richer, but check to make sure you have a gap first. Even increasing your idle speed gets your pump lever closer to contact.
      Ive thought of that also, it has to be pulling fuel feom some where. Ive had the same adjustment on the arm with both nozzles, when i go to the 25 yhe carb shows lean everywhere‍♂️,.. Thats fine i guess cause i found a definate limit but, ive never seen a pump nozzle have such a huge effect. Ill try it again with a larger gap in the pump arm, see what that does.

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