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Thread: air fuel mixture

  1. #1
    Join Date
    Apr 2011

    Default air fuel mixture

    I air fuel mixture is wrong and i need to adjust it but worried about messing it up more. So if i just wanted to lean it out a little which way do i need to turn the mixture screw. my truck stalls when i punch it and occasional backfires, and has alot of black smoke when i gun it. and sometimes when i turn the truck off it still stalls and backfires. I am worried that if i dont lean it out a little it will mess up the motor. i am planing on getting it tuned at my local speed shop, but in the mean time i would like to lean it a bit. it also only gets like 75 miles to a tank of gas, yes a tank of gas.

  2. #2


    In is lean and out is rich
    first get the engine up to temp,
    then kill it,
    then screw the screws all the way in
    and back them out 1 1/2 full turns
    restart the engine,
    with it up to temp and @ idle
    turn one in 1/4 turn then the other one in 1/4 turn
    go from one to the other 1/4 turn at a time
    until you hear a RPM drop
    then back both out 1/8 turn
    oR if you have a vacuum gauge keep all mixture screws the same amount of turns to get the highest vacuum reading
    you can
    Ricky R. Holley tech service

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