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Thread: How do I adjust idle mixture screws to run lean?

  1. #1
    Registered Member
    Join Date
    Dec 2016

    Member #:3243
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    3

    How do I adjust idle mixture screws to run lean?

    My 55 265 V8 with original 2 bbl carb was stalling and hiccuping, sprayed carb with cleaner and filled gas tank, added fuel cleaner. Car ran better during 100 mi drive home, but still wanted to stall on acceleration. Tried adjusting idle mix, problem of stalling fixed, but slow to speed up and acceleration very poor.

  2. #2
    Registered Member BamaNomad's Avatar
    Join Date
    Nov 2016

    Member #:3217
    Location
    Rocket City, USA (Huntsville, AL area)
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    3,774
    If it 'starves' on acceleration, then your accelerator pump might be failing??

    If the car has sat a lot, then your carb probably needs a rebuild...the Rochester 2 bbl is an easy rebuild, and kits are cheap... turning the mixture screws clockwise reduces the fuel, and thus leans it... (I think'm remembering this right!)..

    In Mike's rebuild video below link, he suggests to run the idle mixture screws in (CW) to the stop (gently, not tight), then back out 1-1/2 turns as an initial mixture setting. Once the engine is running, you turn the screws IN until the rpm begins to drop, then back out 1/4 turn. Do that for both screws.

    PS> Kits are about $20... from your local parts store or from Mike's.. here is part 2 of his rebuild video..
    https://www.youtube.com/watch?v=WHuMKvtrbZk
    Last edited by BamaNomad; 12-07-2016 at 10:48 AM.

  3. #3
    Registered Member
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    May 2012

    Member #:625
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    3,409
    Todays fuel is very hard on old accelerator pump boots.

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