Need help with carb running rich, jet size maybe?

Discussion in 'Fox 5.0 Mustang Tech' started by FaTaLAttRacTioN, Jan 27, 2008.

  1. Ok so im having an issue with my new 351w thats been running rich.This is a new motor.Its a 1972 351w block with stock ported heads comp cams 512 hydrolic flat tappet cam performance products intake and a quickfuel 750 carb.The car starts and idles fine but you smell fuel and if you look under the car its just smokey in general.My fuel pressure is weird.I am running a holley fuel pressure regulator into a summit dual feed line.I have 1 fuel pressure gauge on the summt line by the carb and the other on the fuel pressure regulator.Now if i have 3psi at the regulator i have about 13 psi at the summit dual feed line.If i have about 1psi from the regulator im running 7 1/2 psi by the dual feed.Why is this?Which is most accurate?I dont know what else to do in this case.I looked at my quickfuel calibration sheet and it says the following
    Pri Jet: #74
    Sec Jet: #84 W/Jet Extensions
    P.V. Pri: #45
    P.V Sec: Plugged
    Pri Nozzle: #31
    Sec Nozzle: #31
    Acc Pump: 30cc Pri and Sec
    Pump Cam: Pink Pri and Sec position #1
    Idle Air Bleeds: .070" 10-32 Screw-in Type
    High Speed Bleeds: .033" 10-32 Screw-in Type
    Floats: Brass Primary,Nitrophyl Secondary (nothed for jet extensions)

    Anyone with any imput please give me a hand.Im not sure if this is a jet issue or not so any detail and help is much appreciated.
  2. Are you running 2 differant kind of gauges? Are they liquid filled? If they are get rid of them. I've had issues in the past with liquid filled fuel pressure gauges being inaccurate.
    After you get that figured out your going to need to tune your carb. From what I can see it's pretty close. Remember weather will effect your carb settings. A summertime tune will be differant then a winter tune.
    If your not comfortable with tunning a carb get with someone that is.
  3. first get that fuel pressure figured and set it at 6 psi to start. Then put a vacuum gauge on it and see what you have for vac.
  4. running rich at idle

    I have a 91 with holley try this it worked on mine with tunner hooked up set idle screws to 1.5 turns out all 4.change power valve to an 85 go to a 75 jet in rear should be plenty if it stumbles go up on front down on rear jet it should not burn your standing behind it at idle if you have to drill air bleeds out with pen drill.also are your rear throttle plates open same as front.