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  1. #46
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    As per Smitties pics the linkage from primary to secondary is only there to pull the secondary plates shut when you get off the gas. It also restricts the opening rate of the secondary plates with respect to how far the primaries are open. The linkage doesnít Ďpullí the secondaries open like a Holley. The secondary plates only open from inlet vacuum. So say your at 1/4 throttle up a steep hill (high load). The position of the linkage will stop the secondary plates snapping wide open.

  2. #47
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by Str8upal View Post
    "QJ carburetors have mechanical secondary throttle plates operated by a progressive linkage; the primaries open before the secondaries, and use on-demand air valve plates above the secondary throttle plates. The air valves are connected by a cam and linkage to the secondary fuel metering rods. As the airflow increases through the secondary bores, the air valves are pushed down, rotating a cam that lifts the secondary metering rods. The secondary rods are tapered in a similar fashion to the primary metering rods, effectively increasing the size of the fuel metering holes as the rods are lifted and delivering more fuel. Therefore, the position of the air valve will control both fuel and air flow through the secondary venturis, even if the secondary throttle plates are fully opened. Thus the Quadrajet acts like a vacuum-secondary carburetor and only delivers more fuel as it is needed."
    .................
    pretty much what I have been trying to say and show

    the only thing is .... the air valves are sucked down by engine vacuum
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  3. #48
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    ***" QJ carbs have mech secondary throttle plates operated by a progressive linkage"***.

    From post # 45, & 100% correct. I said the same in posts #s 4, 12 & 20.

    Casitron,

    What you said in post #46 is incorrect. The pri to sec linkage purpose is not there to pull the secs shut, although they do that too. Using that logic, the secs on a vac sec Holley would not shut when you lift the #10 off the loud pedal. All American carbs & all others I have seen have the shaft offset in the bore. This is to assist air flow in closing the blades. QJs & Carter carbs also have a return spring on the sec shaft.
    And it is not correct to say the QJ secs do 'not open like a Holley'. According to my Holley book, mech sec Holley carbs start to open the sec when the primaries have reached about 40 degrees of opening. Both pri & sec then arrive at WOT at the same time. QJs work the same; after some amount of pri opening, the secs start to open & both arrive at WOT at the same time.

  4. #49
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    Crikey, I do like the Quady as a carb but Iím about all Quadrajeted out now.

  5. #50
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    So why in the photos are the secondaries not open?

  6. #51
    Do you ever leave? EH179's Avatar
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    Quote Originally Posted by 46Crab View Post
    Crikey, I do like the Quady as a carb but I’m about all Quadrajeted out now.
    Aren't we all.

  7. #52
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by 46Crab View Post
    Crikey, I do like the Quady as a carb but I’m about all Quadrajeted out now.
    so am I......

    black is white, a QJ works like a Holley (not)
    Already been told twice QJ secondarys open at 40% throttle (not)
    and someone needs a eye check (pics are here for a reason)

    next I will have drips under pressure (aka experts) telling me QJs are square bore
    and Holleys not only counterweights, but spreadbores and then two will say
    they are Jesus (one of them is wrong)

    NO further correspondence should be entered into


    so with apologies to our thread starter Snowman
    .... closed
    Last edited by Smitty2; 09-01-2019 at 06:48 PM.
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