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High Idle

Discussion in '40- & 55-Series Tech' started by Bryan-71, Mar 30, 2004.

  1. Bryan-71

    Bryan-71

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    I have a '71 40 with the stock engine, I changed the old carb with one from a 78. The butterfly valves dont want to close all the way, I checked for tension in the accelerator cable and there is none, and I have put a reletavely strong return spring in also. I can pull it closed with my hands, but when I let go it opens right back up. I have completely desmogged the engine, and only have one vaccum line running to the brake booster, and one to the valve cover. Any help would be greatly appreciated.
     
  2. 72cruiser

    72cruiser

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    check your idle screw.

    if it is moving the cam to open the butterfly valves when it is at rest you would be able to pull it closed by compressing the spring on the idle screw. the return spring would not be able to do this b/c it's k value is much lower than the shorter thicker idle screw spring.

    loosen the screw a couple of turns. with the engine off you should be able to look down the barrels with a flashlight and see when the valves are about closed.

    that's my best guess, anyways.

    check with pin_head or degnol, they've been able to help me with my carb in the past.


    malphrus
     
  3. Pin_Head

    Pin_Head

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    Make sure that the throttle positioner is removed or at least back off the screw for the TP. If you don't know what the TP is, check the manual or the SOR online catalog. You may experience detonation/rumbling/backfiring/popping in the exhaust manifold upon deceleration and in between shifts with this carb.
     
  4. Bryan-71

    Bryan-71

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    Thanks for the input guys, I will be working on it this weekend.