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    Centering Butterflys in a Stack Injector

    Centering Butterflies in an Injector:  This is Very important to do correctly

    1. Remove injector stacks.
    2. Remove all external throttle return springs.
    3. Loosen lock nuts and back out idle stop screws on both ends of the injector.
    4. Identify bronze throttle shaft couplers, loosen both Allen screws. (Most units do not have shaft couplers)
    5. Identify the hex link that runs to either side of the injector and the bronze throttle arms.
    6. Loosen the Allen head pinch clamp screw on only one bronze throttle arm.
    7. Loosen all the butterfly screws.
    8. Lightly tap the butterflies closed with your finger while lightly sliding the throttle shaft back and forth against its stops.

    8A. Using a feeler gauge, use .002″ as a measurement at the top side of the butterfly while exerting pressure for Methanol . . When each butterfly is at .002″ tighten one screw in each barrel ( You can use .003″ for Gasoline and E-85  engines   .  For  engines over 450 cu in , you might add .001″   to the settings.
    9. Center throttle shaft side to side. Tighten butterfly screws using caution not to over tighten.
    10. Tighten both allen screws on bronze throttle shaft coupler.
    11. Perform same adjustments on other side of engine.
    12. Tighten the pinch clamp screw on bronze throttle arm.
    13. Reinstall throttle return springs.
    14. Reinstall injector stacks.

    * 2 Medium weight throttle springs – one on each side – is essential to uniform closure of butterflies- DO NOT EVER USE ONE STRONG SPRING

    Butterflies are Beveled-  Hold them up to the light to see the beveled side- the bevel follows the bore in the injector

    15   You do not adjust the idle with the stop screws-  Idle is adjusted by the mixture of the barrel valve-  The stops are meant to keep the butterflies from hitting the walls of the injector.

    Call Mike Chilando  at 615-457-3192  or e mail at  or  with questions