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72 & 83 jetting too rich on 460 Ford 770 Brawler.

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  • 72 & 83 jetting too rich on 460 Ford 770 Brawler.

    I opened the carb today to find a small Allen plug floating around the secondary and a location post broken off of a metering block. I've had the carb for a few months, but took it for the first drive the other day. It ran, but ran like an old truck. Just trash. I pull a plug and it's black. I looked online for jetting suggestions and the suggestions are 74 & 84. Is anyone running much leaner jetting than this? I was thinking about getting jets and trying to find the ones that work. But before I start chasing my tail due to there being a bigger problem with this carb, I thought I'd gather some opinions on it. Another odd thing the carb showed up with the fuel screws only a half turn out. Is that common? That seems to be where it idles. Also the bowls were screwed on so tight that the seals were cut by the bowls. Is this common?

  • #2
    Contact Holley Tech Service (LINK).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crankshaft & H-beam rods, forged pistons, Trick Flow Twisted Wedge 11R 205 CNC Comp Ported heads, 12:1 compression ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI Comp Ported intake, BBK 80mm throttle body, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima 34/78 Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal Dual 12" HP 3168 CFM fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.


    • #3
      Changing the main jets will not affect the idle and light cruise. That's controlled by the idle feed jet, idle air bleeds, transfer slots and idle screws. You're limited to using the idle screws to lean this area out. A power valve has been known to leak and add unwanted fuel. If the carburetor is new and has damage, send it back.


      • #4
        Idle and cruise is fine. But it's slow to rev up. The 1/2 turn out to get a clean idle seems to be too far in according to the videos people have made about tuning the 4150 style carbs.

        I'll contact the tech line today and see what they have to say. I don't want to have to return it. I think I've thrown out the box.


        • #5
          Sounds like you need to find a good carb tuner.


          • #6
            Found a lot of stones in this field. Wow, a culprit that needs to be fixed and tested first are cracking and falling apart vacuum caps that look like they are 10 years old.
            Click image for larger version

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            EDIT: Even thought the caps look bad they don't seem to be leaking a significant amount.
            Last edited by doholleycarbssuck?; 04-04-2022, 11:06 AM.


            • #7
              Since this is refurbished, is there any chance the former purchaser modified the jets and Holley just sets it up to idle and sends it back out and my jet numbers may be lying to me?


              • #8
                "Silicone" vacuum caps last longer. The 80 piece set I got from Ebay works great. Made by Tekz #45253.
                On behalf of every manufacturer, delivery drivers, supply chain representatives, and workers of the world, "We're Sorry."