Idle mixture backing out

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  1. Belvedere One

    Belvedere One Member

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    I inadvertently discovered this issue where all four idle mixture screws had backed out from the 1.5 turns out that they were set at. The carb is Quick Fuel Street Q 950. I re-tested this again yesterday when I set them back to 1.5 turns out and went for about a 6 mile ride and again all 4 corners were out at least two turns. Is there a way the keep these where I want them? Blue Loctite?
     
  2. threewood

    threewood FBBO Gold Member FBBO Gold Member

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    Is there is no spring to keep tension, I wouldn't hesitate to add a small drop of blue locktite to keep them from moving.
     
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    • Belvedere One

      Belvedere One Member

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      No springs. The loctite solution was the first thing that came to my mind but wasnt sure if that is bad idea or not.
       
    • 1 Wild R/T

      1 Wild R/T FBBO Gold Member FBBO Gold Member

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      I don't know about QF carbs other than that they are similar to the Holley design... Holley uses a cork/rubber Screen Shot 2020-11-29 at 8.29.25 AM.png Screen Shot 2020-11-29 at 8.29.50 AM.png ring to seal the screw & provide tension to hold the adjustment...
       
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      • Belvedere One

        Belvedere One Member

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        I'll pull one out and see what material the seal is. I would think the viton or nylon, whatever those are made from in that pic would be far better than cork.
         
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        1 Wild R/T FBBO Gold Member FBBO Gold Member

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        Cork actually has worked pretty well for 50+ years..

        BTW the trick for removing the seals is to back the screw out till all it's threaded into is the seal then just use the screw to pull the seal..
         
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        • R413

          R413 Well-Known Member

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          I would not use any loctite on them. Such a small screw and fine threads How will you Get it move again?

          How about a very small amount of RTV on the last couple threads. We just to add some tension on the screws not lock them up.

          EDIT, yes gas eats silicone, but you aren’t tying to seal anything, just add something to the threads to put some tension on the screw. And you don’t need to go track down the cork seals.

          yes the cork is the correct way to do it, works great.
           
          Last edited: Nov 29, 2020
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          • 493 Mike

            493 Mike FBBO Gold Member FBBO Gold Member

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            Gas and silicone do not mix. Gently flatten one thread on the needle with a small hammer. It will give an interference thread with enough friction to hold your setting and not damage the metering block threads. Be gentle!
            Mike
             
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            • PRHeads

              PRHeads Well-Known Member

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              Are the gaskets seals installed properly, and not hanging out of the recess?

              Remove the screw and the gasket, then reinstall the gasket first. I use a small pocket type screw driver and gently push them all the way into the recess.
              Then reinstall the screw.

              There should be noticeable resistance/drag on the screw if the gaskets are still good.
              If there isn’t...... replace the gaskets.
              The Holley cork gaskets have worked fine for me for 40 years.

              https://www.ebay.com/i/402052725080...MIxtuY1q2o7QIVkweICR33OgdIEAQYAiABEgJ8b_D_BwE
               
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              • Belvedere One

                Belvedere One Member

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                I see nothing out of the recesses but there is definitely little to no resistance on the screws which is why they are not staying in place. I'll order up some new gaskets. I just wonder how well the cork holds up after a short time here in the desert climate.
                 
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                1 Wild R/T FBBO Gold Member FBBO Gold Member

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                Cork works fine, it's all we ever use, the rubber stuff is the unproven option...
                 
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                • PRHeads

                  PRHeads Well-Known Member

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                  There is a cork gasket down inside this recess. It’s far enough in where you can’t even see it in this pic

                  47824EB3-176D-4D05-9C1E-A7223AE434C2.png
                   
                  Last edited: Nov 29, 2020
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                  • Belvedere One

                    Belvedere One Member

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                    They are in there a ways, I'll get a set of those ordered and see if it solves the issue. Thanks for all the replies.
                     
                  • PRHeads

                    PRHeads Well-Known Member

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                    Might be worth a call to QFT.
                    They sell both the cork and nylon.

                    The old style cast Holley metering blocks actually have little “splines” inside the recess to prevent the gasket from turning.
                    Perhaps with the new billet metering blocks, the cork gasket doesn’t provide enough grip to keep the screws from turning.

                    I’d confirm with QFT which style of gasket is “correct” for your carb before ordering anything.
                     
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                    • Belvedere One

                      Belvedere One Member

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                      I checked the QF website but it doesnt list what style is used with that carb so I'll be giving them a call.
                       
                    • Belvedere One

                      Belvedere One Member

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                      I pulled a screw out and they are the nylon version which may be due to the metering block being billet? I couldnt stay on hold any longer with QF but at least I have my answer. The seal came out with the screw so it was not well seated in the block.
                       
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