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Quad to Holly swap-gctid389753

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    Quad to Holly swap-gctid389753

    I have been thinking about this swap, I've read a lot of threads on here about swaping the Quadra-jet to Holley. All the Holley's mentioned (model 4175) have electric choke. My quad is thermostate choke, is there a Holley model that has one or is there a way to adapt the electric choke. & How tall of an adapter do I need to clear the thermostate housing. where's a good buy? There's one on e-bay for $230, But I'm leary, any other ideas?

    Hopefully others that have done this will chime in,

    Thanks all,

    Happy Boating,

    jb

    #2
    Explain "quad is thermostate choke"!

    A Rochester Q-jet in this year range should have an electric Helix heating element to pull the choke OFF.

    In the older applications, you'll see two styles of choke pull-offs.

    One....., the above Helix Heating element, and two......., the Helix in the intake manifold.

    However, by 1987, I don't believe that any straight manifold heat Helix styles were being used.

    None-the-less, the Spread Bore Holley should be a good replacement for you.

    .
    Rick E. Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

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      #3
      Thanks Rick, Well if I remember right I believe it sounds like the Helix Heating element where mine is in the manifold. I will have to check to be certain. But I know it's not electric. Who knows what has been done by the previous owner. I'm still trying to figure it all out. What options would that leave me?

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        #4
        Surf137 wrote:
        Thanks Rick, Well if I remember right I believe it sounds like the Helix Heating element where mine is in the manifold. I will have to check to be certain. But I know it's not electric. Who knows what has been done by the previous owner. I'm still trying to figure it all out. What options would that leave me?
        The Helix itself is all mechanical. It's nothing more than a helical wound spring affair that reacts to heat. It opens and closes the choke plate by way of a linkage.

        When cold, it pulls the choke ON (closes off the choke chimney).

        When the Helix is mounted in the intake manifold, the exhaust cross-over provides the heat to it in order to pull the choke OFF.

        This is sometimes refered to as a "divorced" choke.

        When the Helix is carburetor mounted, an electric element is used to provide the heat to it in order to pull the choke OFF.

        This is all pretty much moot since the Spread Bore Holley (I believe) will use the electric choke exclusively.

        .
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment

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