Quick fuel carb fuel pressure too high? Rich idle...

Fuel and Air Systems

  1. yellow rose

    yellow rose Overnight Sensation FABO Gold Member

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    Both sides. I’m not sure on those metering blocks, but you may have to tap the lower holes to 6-32 to lower them.

    I have no idea why they all run the IFR’s up there. They really need to be in the lower position.


    I’ve tired my junk with them high and low, and my deal liked them up.

    Now, I’m thinking my tuning was off in other circuits, causing the carb to want the IFR’s up high.

    So I think I’ve corrected my tuning sins, and I have them lowered. And, unless it absolutely won’t idle correctly, I’m going to leave them down.

    The science behind low IFR’s has long been settled. And if you think about it, the science makes sense.
     
  2. cawcislo

    cawcislo Well-Known Member

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    I’ll pull my bowls and look at my Billet metering blocks and see what needs to be done to lower them. Thanks for the advice. I’ll post results once completed.
     
  3. crackedback

    crackedback FABO Gold Member FABO Gold Member

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    Lowering float level a flat or two can clean up the idle as well.

    Have to try it to find out
     
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    • cawcislo

      cawcislo Well-Known Member

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      I’ve already lowerd it to 1/3 of the glass sight plug, how much lower can I go?
       
    • cawcislo

      cawcislo Well-Known Member

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      I pulled the metering block. It looks exactly like the pic here which is a bare quick fuel billet metering block. So it looks like I would need to tap the hole on the bottom in order to move the idle feed Restrictor. Is my schematic correct below. I believe so as the old Holley carb has the restrictor (permanent) in that position (the bottom holes). Wish they would have tapped it at the factory....

      F65F37C7-53F1-429A-8F05-55D39C4A5A60.png
       
      Last edited: Nov 4, 2020
    • yellow rose

      yellow rose Overnight Sensation FABO Gold Member

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      Yes, that’s what you need to tap. I wish they would tap the lower holes too, but I’m putting together a brand new carb, all billet and I have to tap the lower holes.

      It sucks, but it’s worth it. Also, a spiral fluted tap is a bit easier to use in this application.
       
    • cawcislo

      cawcislo Well-Known Member

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      Okay tapped the new holes in my metering block, that was pretty easy with the spiral flute tap I bought. Had to enlarge the area around the tapped hole as the idle feed restrictors need a bit more room to screw them in. So I got it done. But are they low enough. Not much clearance between them and the gasket that will be installed. Let me know what you think.

      F2E2BEC5-C574-447F-A263-C0ED78F51E44.jpeg

      4A082005-A343-43D7-AAC7-17D04CBB0654.jpeg
       
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      • 67/6barracuda

        67/6barracuda Well-Known Member

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        I need to do the same thing. I have a thread where I was tuning all summer with frustration. Could not get it right. where did you get the spinal fluted tap? What size and and part number?
         
      • cawcislo

        cawcislo Well-Known Member

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        Amazon is where I bought the tap. It’s a 6-32 size. I’m sure there plenty of other places to buy from. Just take your time with the tap. I used some cutting oil and went forward just a little then backed it out a bunch, back and forth I didn’t want to break the tap off. But it went well and was fairly easy.

        EAFDECDC-198D-4DAC-80BE-A3C3CD461A00.png
         
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        • yellow rose

          yellow rose Overnight Sensation FABO Gold Member

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          Perfect. The only thing I will mention is if you don’t want to do the extra clearance work for the jets with the screwdriver head on them, you just use brass 6-32 x .125 long set screws.

          Otherwise, you did good. And that’s not wrong what you did, just a bit more work if you like the screwdriver headed jets better, use them.
           
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          • cawcislo

            cawcislo Well-Known Member

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            So the jets are deep enough as is? Just want to double check before I toss it back together and reinstall it.
             
          • yellow rose

            yellow rose Overnight Sensation FABO Gold Member

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            Yep, that will work.
             
          • 67/6barracuda

            67/6barracuda Well-Known Member

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            Checking in, did you test now that you moved the IFR’s down?
             
          • cawcislo

            cawcislo Well-Known Member

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            Sorry, I haven’t been able to do any additional testing. The snow started to fly and the temps dropped so I have not been too motivated to do any more wrenching before winter. If we get any days that aren’t too cold I may fire it up and see how it idles, although it should have leaned out a bunch just from the 40 degree F temp drop since the last time. :)

            but fear not I will not let this post die until I jump through all the hoops with this carb. Hopefully I get it dialed and can share my learnings with others.
             
            Last edited: Dec 10, 2020
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