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tech question- quadrajet mulitple choice

Discussion in 'The Hokey Ass Message Board' started by praisethelowered, Jun 16, 2005.

  1. praisethelowered
    Joined: Aug 14, 2003
    Posts: 1,103

    praisethelowered
    Member

    The is the first time I have ever installed a new quadrajet carb without having an existing set-up around to go by . . . so I am putting the question to the hamb.

    What are all of these vacum ports for?

    Specifically I need to hook up the vac. advance on the HEI and the vac. line that runs to the carb. . . but whoever can label them all wins.

    The prize is the warm fuzy feeling of being cooler than some dope in CA that doesn't know one from the other

    The first pic is from the passenger side front.
    The second pic is a view from the drivers side rear.
     
  2. Upchuck
    Joined: Mar 19, 2004
    Posts: 1,576

    Upchuck
    Member
    from Canada BC

    heres how mine hooks up don't look excactly like yours

    [​IMG]

    [​IMG]

    I hope that at least helps a little:D
     
  3. praisethelowered
    Joined: Aug 14, 2003
    Posts: 1,103

    praisethelowered
    Member

    You know I'm blown away that a guy half a world away would take a photo and label all that stuff. . . really cool.

    But your quadrajet is just different enough that it doesn't seem to translate.

    For instance your vac. advance comes off ta small port at the base and in that same spot mine has a tube sticking out that is about 4 times bigger. . . so that doesn't seem right. . .

    can anyone shed more light on this?
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 50,245

    squirrel
    Member

    you should use either A or C or E for distributor vacuum, depending on if you want ported or not. You'll have to test them by sticking your finger over the tubes to see if they get vacuum at idle or not. Consensus is that full vacuum works best for the vacuum advance, so find one of these 3 that will give vacuum all the time, and connect it to the distributor. My guess is that A will be it. Plug off the other two.

    F is for the PCV valve.

    B is for the choke supply, I think, plug it unless your automatic choke mechanism needs it.

    D looks like a bowl vent, if it's big, that should be what it is. I assume this is going in a hot rod, not a smog car, so plug this one also.

    hopefully this will get you close.

    Also check to see that the threaded hole in the bottom, rear center is plugged, where Upchuck labeled his "brake booster". unless you have power brakes you need to supply with vacuum.
     

  5. Most California dopes - me bein one and all - would get a vacuum gauge and find out for themselves....
     
  6. DrJ
    Joined: Mar 3, 2001
    Posts: 9,418

    DrJ
    Member

    Or, if the carb's off the manifold, some of us California dopes who might want to know what the ports do before the engine's running would get a length of clean rubber hose and hook it to various sources and blow air thru them to see where it comes out inside the carb.
    Like if it comes out up in the venturi above the throttle plates, plug it.
    If it comes out a hole or opening below the throttle plates it's for Vacuum Brake Booster , or PCV Valve (the two big ones in the middle,one front one back) or a small one to the distributor Vac. adv.
    If it's got one that vents the float bowl, it's supposed to have a hose going to the stock air cleaner. Leave it open if using some other cleaner or the float area won't get the ambient air ressure it needs to work right.

    I'm curious as to what car that carb is from (what's the number stamped vertically on the drivers side just aft of the secondary throttle levers?)
    Most of the Qjets I've seen have that vacuum pot in front of the choke by the inlet that Upchuck's has.
    I don't think I've seen two different engines with the same exact Qjet carb, weird huh?
     
  7. praisethelowered
    Joined: Aug 14, 2003
    Posts: 1,103

    praisethelowered
    Member

    Thanks all.



    This will the first start-up for this motor after an external re-build (removed all the smog, new distributor, carb, headers) and so I want to set up everything as right as possible before I turn the key. Since dist. timing is a shot in the dark I want to reduce the variables.

    I guess I am more in the dark than you guys think. This is also the first HEI I have run. . . they need ported vacum for the advance right?

    Anyway, between upchucks photos, squirels recomendations and DRJ's how-it-works I should be able to get it going.

    Thanks again.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 50,245

    squirrel
    Member

    Not necessarily.
     
  9. Richard Head
    Joined: Feb 19, 2005
    Posts: 522

    Richard Head
    Member

    Vacuum advance should be connected to a timed vacuum port which means no vacuum at closed throttle. These are usually at the bottom of the carb near the throttle plate. My vote would be port E.


    If the quadrajet is from a mid 80's car it may not have a vacuum advance port because the distributors had electronic advance. They are easy to spot because they have an electrical plug in the top of the carb body. I just threw one away this week.

    Dave
     

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