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Qjet compatibility & CA emissions, Choke, Dieseling

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 77Jimmy, Sep 4, 2002.

  1. 77Jimmy

    77Jimmy 1/2 ton status

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    Qjet compatibility & CA emissions
    The 77 Jimmy 350 4bbl I recently purchased has a non-stock rebuilt Qjet on it (it has a rebuilt sticker on the back). The number on the carb is 7044526. If I’ve done my homework, this is a Qjet for a 1974 automatic Chevy 350. My concern is the 5 digit which I believe means CA emissions.
    Questions:
    1. Is this carb safe to run on my motor?
    2. What carb specs do I use, meaning do I use the specs for that carb or the specs for a comparable 1977 carb? Where can I get specs for that carb? It’s not listed in Chiltons or Haynes.
    3. How can I tell if my vehicle originally had CA emissions? I’ve searched high and low for the emissions sticker that Chiltons and Haynes says should be in the engine compartment but it’s no where to be found. Is there an RPO code for this? I have the original RPOs for the vehicle but I don’t see one on there for CA emissions.

    Choke
    Engine is a bit hard to start. I pump the gas pedal 3 times and crank the key. Usually it takes about 2 or 3 more pumps after that to get it fired up. Once fired up it wants to die so I have to pump the gas pedal and rev the engine usually 2 times to keep it from cutting out. At that point, the engine is running on its own, low RPMs, and then idles/warms up and runs fine.
    Questions:
    1. Is this a choke problem?
    2. Any other thoughts?

    Dieseling
    I’m experiencing some dieseling. I have taken Grim’s advice from a previous post and have put some STP fuel cleaner (silver bottle) in the gas tank. Am hoping that solves the problem. If not, next step will be to try a 91 octane gasoline.
    Questions:
    1. Sound like a good gameplan?
    2. Just curious, what octane is everyone running?

    Thanks!
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    You won't hurt the motor, as long as its not running too lean. If it were a 6 cylinder Q-jet, I might worry about that, but driveability would suck anyways.

    Sounds to me like you have a vacuum leak or mal-adjusted choke. Hows idle once it warms up, in gear? What RPM?

    Unless your engine is fairly stoutly built, 91 is a waste. 91 burns slower than 87, and doesn't do anything (actually tends to hurt power) if the engine isn't designed for it. (higher compression) You'd only be masking the problem by running 91. Hows timing?

    I run 87 octane in my 350, and ran 87 octane in my 305 which was (stock) 9.2:1 compression. My new 350 should come in right around 9.3:1, and I'll still be running 87.

    I get 18MPG freeway, 13 city and don't drive conservatively in town. My truck never diesels, idles perfect, and is not hard to start.
     
  3. 77Jimmy

    77Jimmy 1/2 ton status

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    Idle is fine when it warms up. Don't have a tach hooked up yet -- on my list of to do's. (Any recommendations on a tachometer? Is a tach from NAPA just as good as any other?)Idle doesn't seem to be high or low just from the sound of the engine.
     

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