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Q-jet computer problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rjfguitar, Sep 24, 2002.

  1. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

    Aug 28, 2002
    Likes Received:
    I have an 85' k-5 with the california emissions equipment and the computer contolled Q-jet. My problem is that I am building a performance 406 SB that will need more carburation than the old 350 but no aftermarket companies make a computer controlled performance Q-jet.What can I do to get a better performing carburetor? Any Suggestions???
  2. tipoil

    tipoil 1/2 ton status

    Jul 30, 2002
    Likes Received:
    canada guebec
    just look at the secondari(rear top plate) and push in it to see if they open all the way close to 90 degre .
    if not grind the stop on the right side that stop it from opening and that all!!! i thing (not sure exactly but those carb are rated a 600+.- cfm and if it open all the way u are going to have 750 or 800 cfm depending on the size of the primary.
    if i just confuse u more then pm me and i will try to sort it out
    i think that"jet" make a feed back carb whit some goodies allready done but not sure.
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Feb 17, 2000
    Likes Received:
    Are you sure you have a CCC carb and an actual computer, throttle possition sensor on the driverside of the carb with 3-4 wires, O2sensor and not just a carb with a Mixture solonoid? Reason I ask is nobody I have talked to has actually seen the CCC on a truck. It seems that at least in the rest of the country they just have the mixture control carb. The only thing that controls the mixture control set up is a thermostatic switch on the intake manifold. If you have that set up you can get a Carb off a 81 or so and it will have all the connections for the rest of the emmisions except the mixture control solonoid and unless they check the actual carb number they will be none the wiser. I have never had problems getting my Quads to pass emmision. Heck it passed the sniffer a few years back with NO cats. Now our Nazi are nowhere as anal as the ones in Cali. If it passes visual (EGR, Cats, Flap in the fillneck) and it passes the sniffer then they don't care about anything else like E0 numbers and junk.
    Other than stops the Quad will flow 750CFM on the small one and 790 or something on the big one. The quad you have now should be able to handle the engine if it's running ok.
  4. Blue85

    Blue85 Troll Premium Member

    Jul 26, 2000
    Likes Received:
    Grand Rapids area
    I had almost decided that the computer controlled carbs never went in trucks, but now I know that at least in California, some did. Are you sure it's a computer carb, though? It should have a solenoid on the passenger's side and a throttle position sensor on the driver's side. A lot of non-computer carbs had some other wires coming out that often confuse people.

    I don't know of anything that would keep you from working that carb into something that the 406 could use. I would just worry about the ECM programming.

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