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Thread: Rochester quadrajet secondaries never open kickdown downshift never occurs

  1. #1
    Join Date
    Apr 2009
    Location
    Houston
    Posts
    95

    Default Rochester quadrajet secondaries never open kickdown downshift never occurs

    79 345 auto. My secondaries never open. Kickdown downshift on occurs once in a while. I am new to carbs. Is there something simple to adjust. Not sure about vacuum but timing is 5 btdc. It cruises really well but I never really get a sudden burst of power. Thanks in advance.
    Last edited by jtl1100; 08-23-2009 at 04:35 AM. Reason: Misspelling

  2. #2
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    There is a kick down linkage that goes back to the transmission shifter from the throttle linkage. It may be that this linkage is out of adjustment. The carb has vacuum secondaries, and it only uses as much secondary as it needs. It may never kick down all the way until you get into passing gear at higher speed.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  3. #3
    Join Date
    Jun 2009
    Location
    Little Rock
    Posts
    40

    Default

    I disconnected my kickdown lever and just shift it like you would manual. This way you can control the tranny downshift for passing,and use the braking action of the tranny to help stop. I prefer it over the mechanical linkage.

  4. #4
    Join Date
    Feb 2009
    Posts
    4

    Exclamation adjustments

    You have to adjust the secondarys so that they will open right. There is a small screw and lock screw on the pass side of the carb. Lots of info on my web site on q-jets. And don't unhook the kick-down linkage, It controls more that kick-down. It also controls internal pressure, unhooking it will in time burn up the trans because it will run low pressure. Get a factory manual and adjust it right. From what you are saying adjust the KD rod to make it "longer", that will increase "up" shifts and give you downshifts.
    Scott


    http://home.mchsi.com/~s2doc/

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