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Q-Jet ported/manifold vacuum port locations

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BorregoK5, Feb 27, 2002.

  1. BorregoK5

    BorregoK5 1/2 ton status

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    Frankly, I'm a Holley guy but lets face it, Holleys don't do quite as well as the Q-Jet off road. So I bailed my Puddle Dumper for this Q-Jet and it works oh so much better at angles and across the washboards. I've been using my vacuum advance off manifold vacuum up until now where I'm dialing in my advance curve. I'm not too familiar with my Q-Jet which leads me the the big question.

    Looking directly at the carb from the radiator I have two smaller vacuum ports. One on the front(centered to the right which I think is ported vacuum) and one on the left side of the carb (with a 1 1/2" long snout near the front of the carb) which is direct manifold vacuum. Can someone verify that the first of the two is ported vacuum meaning that it has no vacuum at idle but only at part throttle on up and that this is the correct location for my vacuum advance?

    I started with nothing and I still have most of that left! - <a target="_blank" href=http://community.webshots.com/user/borregok5> Pictures</a>
     
  2. BorregoK5

    BorregoK5 1/2 ton status

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    I found an answer elsewhere and yes, the second option above is ported vacuum.. post closed!

    I started with nothing and I still have most of that left! - <a target="_blank" href=http://community.webshots.com/user/borregok5> Pictures</a>
     
  3. Blazer1970

    Blazer1970 1/2 ton status

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    QJets vary from year to year on what ports are what, and all ported vacuum ports are not created equal. Best way to tell what you have is to use a vacuum gauge. They are inexpensive to buy, and cut out the guess work.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  4. BorregoK5

    BorregoK5 1/2 ton status

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    I know, I always used my neighbors vac guage and he moved. I got to get off my but and go get one of my own. I bought a book on Q-Jets and not one of them looks anything like mine in the breakdowns (at least not to a level thats helpfull).. dangit!

    I started with nothing and I still have most of that left! - <a target="_blank" href=http://community.webshots.com/user/borregok5> Pictures</a>
     

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