Explain it like I'm 5: Carburetor Linkage Confusion
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Thread: Explain it like I'm 5: Carburetor Linkage Confusion

  1. #1
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    Explain it like I'm 5: Carburetor Linkage Confusion

    Hi,

    My 69 Cougar 351W came factory with a 4 barrel, but PO put a 2 barrel Autolite 2100 on it. I was struggling (stupidly) for a while trying to understand why my brake pedal was "so low to the floor" when suddenly I realized it's the gas pedal that is way up higher than it should be. Tracing things back, best I can tell is that if the linkage on the gas pedal was closer to the accelerator cam on the carb, my pedal should move lower to the floor.

    So, does it make sense that if the PO used the 4 barrel throttle cable bracket instead of a 2 barrel bracket this would happen? Seems to me the length of the cable doesn't matter, just the position where it would be 'locked down' on the manifold. Correct? Is there a length that it should be that I could check to see if this is the issue?

    I did a bit of googling but I don't even know the right terminology for what part I have to change to get the distance correct. Where do I look to get a new bracket if this is even my issue?

    Secondly, it seems my kick down linkage also doesn't line up. I just had the tranny rebuilt and just now noticed that the kick down is already starting a tiny bit engaged (not long enough to be pushed all the way forward). The tranny is shifting oddly. Are there different lengths for that kick down rod for a two barrel vs. a 4 barrel? Where does one purchase a different size? Or do I crawl down there and bend the rod to make it line up better?

    Thank you in advance! I've always been a bit hesitant to mess with carburetors due to my lack of knowledge.

    Bonus question: if I want to put an aftermarket intake and 4 barrel carb, do I necessarily also have to change the camshaft to match? (I don't know if this is a 2 barrel motor swapped into the car or a different manifold and carb - I assume no one would "downgrade" to a 2 barrel so I think its an engine swap).

  2. #2
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    Let's see a photo of what you have for linkage so that we can identify what it is or isn't.
    Royce Peterson
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  3. #3
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    Thanks for the quick reply! I went to take the pic and also searched "bracket" on WCCC and I think I see my problem. Definitely the wrong bracket. Mine is out about 2 extra inches. Also, I see on WCCC that the kick down is one size for the 2V or the 4V. I will have to see with the new bracket if it fits better (bad bracket may be touching it).

    But it does prompt another question: should the kick down cam have a spring on it holding it towards the front of the car? I do not see anywhere to put a spring. (no bracket). I rigged something up assuming it should. Also, I had to add a looooong screw in the linkage to get it to kick down. Don't laugh at me for my ignorance :P

    Click image for larger version. 

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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    It looks like the PO messed up the geometry a bunch. This is a correct 2V bracket.
    Click image for larger version. 

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    Is the original 4V intake manifold under that steel plate? If so I don't know if going with this bracket would help any. And the kick down rod is not the same for a 2V and 4V application. I know when I put a 4V on one of mine I had to add an adapter to get it where it belonged and working correctly. But that made the original 2V one longer.
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  6. #5
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    Thanks! I ordered that bracket from WCCC last night. I also found a holley video that mentioned the adapter for the kick down to extend it if going to a 4V, so it looks like my kick down shaft is the right one. I also saw on that video how to set the kick down adjustment and discovered I (by guessing) set it to kick down way too soon, causing my weird transmission problems (having just had the tranny rebuilt and not being happy with the results). Finally, I also figured out that with the wrong bracket, I cannot get to FULL THROTTLE, which is why the kick down was feeling very disappointing. I think this one bracket is going to solve everything.

    I am assuming the 2V is mated with the correct input manifold as the 4V has a different opening/bolt pattern.

    When you went from a 2V to a 4V did you also change the cam shaft? Or just manifold and carb? which carb did you choose?

    Thanks again!



    Quote Originally Posted by badcatt View Post
    It looks like the PO messed up the geometry a bunch. This is a correct 2V bracket.
    Click image for larger version. 

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Size:	42.6 KB 
ID:	101553
    Is the original 4V intake manifold under that steel plate? If so I don't know if going with this bracket would help any. And the kick down rod is not the same for a 2V and 4V application. I know when I put a 4V on one of mine I had to add an adapter to get it where it belonged and working correctly. But that made the original 2V one longer.

  7. #6
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    It looks like installing a 4V carb would solve most of your problems. A different cam is not necessary when changing carburetors.
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  8. #7
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    Yes the linkages and brackets are different for 4v and 2v setups. You really need to get the correct 4v bracket and throttle cable to get the geometry correct for a 4v stock or aftermarket install.

    Good news is that Lokar has a version that works and is adjustable as well
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  9. #8
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    Re: Explain it like I'm 5: Carburetor Linkage Confusion

    Thanks. As an update: I bought the 2V bracket from WCCC and it fixed several things: Pedal went back closer to floor, tension on pedal is more correct feeling (though I had to modify spring for new bracket), and I can stomp down to get wide open throttle. Also allowed me to set the kick down to a better position. Spent some time learning about and adjusting carb over the weekend and all combined it made a hell of a difference.

    Just another example of attacking each "system" of a used car, learning everything possible about how its supposed to be set up, and bringing everything back up to spec. What a good feeling on each test drive!

    Thanks all!



    Quote Originally Posted by dfwcatsclub View Post
    Yes the linkages and brackets are different for 4v and 2v setups. You really need to get the correct 4v bracket and throttle cable to get the geometry correct for a 4v stock or aftermarket install.

    Good news is that Lokar has a version that works and is adjustable as well

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