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Vacuum advance port on Q-jet??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by pilgrim, May 30, 2003.

  1. pilgrim

    pilgrim 1/2 ton status

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    Ok this is driveing my nuts or maybe NOT driveing is more like it. I have thumbed through and i'am now seriously reading doug roes book on Q-jets but i can't find any info on WHERE the vac advance is supposed to hook to the carb?? does anyone know???? /forums/images/graemlins/confused.gif

    Vacuum advance theory 101 needed here /forums/images/graemlins/smirk.gif.. My understanding is that the vac advance provides something like 6-10 degrees advance. but that its not "supposed" to do this at idle. rather as vac signal drops, advance is brought in, right. However i can't seem to find a port on my "new" edlebroke Q-jet that does this.. Maybe i have this all wrong and that the vac adavance is supposed to provide advance at idle and drop to nothing when you jamb the gas.

    Someone help me understand this /forums/images/graemlins/smirk.gif

    By the way the reason i'am looking this over is my engine loose's power i a big way when gas is applied say when i'am cruiseing up a hill. hesatates and stumbleing.. when i cup my hand over the carb the rpm's seem to go up, maybe this is a vac leak but i can't find one /forums/images/graemlins/angryfire.gif. maybe its internal /forums/images/graemlins/confused.gif

    thanks /forums/images/graemlins/thumb.gif
     
  2. win717

    win717 Registered Member

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    I put an edlebroke Q-jet on my 1979 blazer bout 2 weeks ago and I pluged the vacuum adance line on the passager side of the carb I believe,there were to more holes in the front and i plugged them,Mines seems to run good
     
  3. jakeslim

    jakeslim 1/2 ton status

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    I also put in an edelbrock carb a few months ago. At first i ran the vacuum advance to the front of the carb. I was having some problems though. I moved to the passenger side of carb and now all is better. Not sure why this is. It is supposed to go to the front port on the carb, but why mess with it now.
     
  4. wrathORC

    wrathORC 1/2 ton status

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    You're choking it out when you put your hand over the carb... of course the RPM is going to go up.

    Anyway, look for "ported" vacuum. To find ported vacuum, use a vacuum gauge. You plug it into all of the vacuum ports on the carburetor until you find one that only has vacuum when you open the throttle valve (rev the engine). It'll probably turn out to be the one on the front of the carb on the driver's side.
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Edelbrock part # 1901 and 1902 should be hooked up to the port on the front, right side of the carb on the fuel bowl. #1903,04,06,10 carbs should connect on the front, bottom, left of the carb on the baseplate. All ported vacuum does is just draw from a slot in the throttle body (base plate) of the carb. At idle, the throttle blades cover this spot and the slot is exposed as the throttle blades open. Plese don't listen to the people that say this is wrong and it will somehow draw too much advance at WOT (it doesn't). Its located in the throttle body, not the venturi people /forums/images/graemlins/rolleyes.gif.
     

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