78 carb settings for timming

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wazzabie, Jul 3, 2002.

  1. wazzabie

    wazzabie 1/2 ton status Premium Member

    Apr 17, 2001
    Likes Received:
    Washington State
    Any one know how to set the carb settings for a 78 350 V8?

    The manual talks about using propane. Is that needed?

    Here is basicicly what the carb looks like

    |-----| |-------|
    | |

    ^|^ these things are the needles

    I think there are sonme other needeles else where? Not sure though.

    What does the left and right one do each? Turning them clockwise does that make them more lean? Can I do this by setting a rpm gauge? What rpm sould it be at?

    Thanks for the help
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    If you are talking about a Q-jet, and likely some other carbs, those are the idle mix screws as best I can tell from your description ; ) Obviously, they affect idle, and thats it.

    Lean them out (screw it in) until the motor starts to stumble, back it off until it smooths back out, then do the other side. Repeat until they are as far in as possible without a poor idle. Adjust idle speed as necessary on the drivers side (one screw) while doing this, and re-time when done. (I would anyway, if the carb is all out of wack, so is timing probably)

    You could use propane, but the above method works for me.

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