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Using computer controlled Q-Jet on non-computer motor?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Stoopalini, Jan 17, 2005.

  1. Stoopalini

    Stoopalini 1/2 ton status

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    Can a Q-jet designed to work with a computer be used on a non-computer motor?

    I recently purchased a Q-jet off of an '84 Camaro and did not know it was one of the computer controlled carbs. Can I make this work on a Edlebrock Performer manifold on a non-computer motor?

    Thanks,
    Thomas.
     
  2. sled_dog

    sled_dog 1 ton status

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    I don't really know, I know my buddy had one of them on his old cop car, he removed the o2 sensor, it ran just like it still had the thing, though it put up a service engine light once in a while.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    It will work, but the "fail mode" of these carbs is full rich on the primaries.

    I had a bad ECM in my '85 Olds Cutlass, and with a 307, 3.42's, and OD, I couldn't get but 10MPG out of the car with the carb running like that.
     
  4. Stoopalini

    Stoopalini 1/2 ton status

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    Thanks Dorian.

    Isn't the 'fail mode' determined by the ECM/PCM though? Or does the carb default to full rich when the connector is disconnected?

    I guess if I wanted to use this carb, I could install an O2 sensor after my Y pipe and hook up an ECM to control it.

    Oh well, maybe I just keep looking for the correct Q-jet for my motor ... although an O2 controlled mixture would be nice ...

    Thanks,
    Thomas.
     
  5. beater_k20

    beater_k20 Banned

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    is this "computer controlled" carb the one with the 2 prong plug on the passenger side front of the carb?
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, I assume those primitive ECM's also had a limp mode, but even if they didn't, the mixture control setup is still spring loaded...without the solenoid "pulsing" (disconnected from the ECM) to meter fuel, the needles just stay all the way out of the jets.

    In the same Cutlass that had the problem with the ECM, I have swapped in a 403 for the 307. However, I still want(ed) to run the CCC system, and was planning on making it work. There are a few variances in the "calibration" internally of the carburetor, so making one work on other engines is "iffy" at best, and will take some serious effort.

    IMO at this point, fitting TBI or multi-port is about as much effort, with more gains. That may end up being the route I take. Just sorry you got stuck with one of those carbs. At one point a few people were working with these things, but as they came to know the ECM's, and the effort it would take to make the primitive systems work how they wanted, it seems to have been decided that a TBI or multiport retrofit would be "easier" since the ECM portion has already been well documented, and more and more injection stuff is coming out that makes retrofitting even easier.
     
  7. trailblazer86

    trailblazer86 1/2 ton status

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    Where does the harness connect?
    Most quad's are not really computer controled.
    If you just have two wires on the front right corner of the carb, this just regulates the volume of the fuel from the accelerator pump.
    Follow the wires and see if it runs to a sender on the intake manifold or on the thermostat housing.

    This is what regulates the power to the accelerator pump. The fuel charge is larger when the engine is cold. Therfore if you leave the wires unhooked you get a bigger "squirt" from the pump.
     
  8. Stoopalini

    Stoopalini 1/2 ton status

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    Thanks guys.

    This carb has a 2 prong blue connector on top and a 3 prong white connector in the front. Pretty sure it's an ECM controlled carb, but maybe not :confused:

    I ended up ordering one of these SMI Carburetors. Little pricey, but well worth it; especially when you consider I will be breaking in a new motor with it :cool1:

    Thomas.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    The three prong plug is TPS, that is without question a CCC setup.
     
  10. R72K5

    R72K5 Banned

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    better known as electronic spark control, 81 82 etc, gm made badges stating such on the trucks,

    thjeres a control module its under center of dash near pedals assembly standing up on its end, cant miss it

    the carb will run rich by default,

    need to have entire system connected for it to work and not run rich all the time, that includes the 7 wire HEI and all the sensors and harness and module

    good luck..
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    ESC is a standalone system (electronic spark control) when badged as such, has nothing to do with CCC, computer controlled carb.

    CCC typically incorporates a knock sensor, although apparently not always, as some (all?) CCC *trucks* have no knock sensor. Believe knock sensor (ESC or CCC) was used based on 305 vs 350, since the 305 compression was "much" higher than the 350 the same year.

    I don't believe CCC was used on trucks until the mid-80's, but started in all US GM *cars* 1981, first year with limited use was 1980.
     

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