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Quadrajet question

Discussion in 'The Garage' started by mo'gas, Apr 4, 2004.

  1. mo'gas

    mo'gas Registered Member

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    I have an 85 'burb and I was considering buying an Edelbrock Quadrajet.
    The Quad I have has two wires that attach to the front right top corner of the carb one wire goes to a sensor in the thermostat housing and the other wire is from the harness. What is this all about???
    I know that they are not for the choke or A/C solenoid.
    If I put a different Q-jet on from an earlier model or an Edelbrock Q-jet, will I regret it?
    The new carb will be going on an Edelbrock non egr manifold.

    Thanks,
    Dave
     
  2. GMCLegacy

    GMCLegacy 1/2 ton status

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    you have an electronically controlled QJet. not the most desirable Qjet out there.

    Personnally i wouldnt buy an edlebrock qjet. i am sure many people have bought them and they were a "bolt on operation." they are not worth the money to me.

    i would buy a early to mid 70's qjet with an external choke from the junk yard and rebuild the qjet yourself for less than 50 bucks.
     
  3. mo'gas

    mo'gas Registered Member

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    It actually runs pretty well but the thing floods during the first start of the day. I noticed that the wire to the thermostat housing is broken. Maybe that's part of the problem?
     
  4. florida4x4

    florida4x4 1/2 ton status

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    It's an electronic q-jet. pretty sure you will have to get a normal HEI if you remove it for a edelbrock. I agree the edelbrock is high priced but it may be worth it after you get the j-yard carb straightened, throttle shafts bushed, and purchased parts to tune it. check out ebay and get a used edelbrock qjet then purchase the strip kit (rods, needles, springs and jets) and start tuning.

    Here is some helpful links I have gathered:
    http://www.florida4x4.com/tech/quadrajet/
     
  5. mo'gas

    mo'gas Registered Member

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    I have seen the full electric q-jets in the past. Usually they have a few plugs going into them other than choke/AC solenoid. And I think those are the ones that need the special HEI. My distributor looks "normal"
     
  6. florida4x4

    florida4x4 1/2 ton status

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    oh ok, then it the one with an electronic accel pump helper, IIRC. They made em for only a couple of years and only on trucks.. That carb is buildable with the same techniques as earlier carbs. should have paid more attention /forums/images/graemlins/doah.gif

    The best carb for your vehicle is OEM. Build from there and save a bunch of guess work.
     
  7. R72K5

    R72K5 Banned

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    EST system, began in 1980 on cars and 1/2 ton trucks, the carb is E4ME

    E for electronic control and other E for electric choke

    very common and very undesireable

    the wire to temp sensor to carb tells the carb how much fuel to dump in at certain engine temps, unplug it and it will run rich as default
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    That dual capacity pump is for cold engine operation, I say fix the wire and just see what happens. Problem may just go away. If it does, if you want to rebuild a carb, I say get a "standard" core (unless required by visual emissions check) as if you ever have to fix that pump, it will probably be expensive, or difficult to find. (although checking this first may be a good idea)

    I don't think many on this board have real experience with this setup. It seems pretty basic (it's not the full electronic system) so it should be pretty simple to understand. I believe that dual capacity pump is just an on/off deal controlled solely by the temp switch.
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    If you wanted a rebuildable core, I have one from an 83 . Its in Mesa AZ. It has the bowl vent for your vapor canister , but NO computer controls. It needs throttle shaft bushings, but if you came calling its here. /forums/images/graemlins/thumb.gif
     
  10. florida4x4

    florida4x4 1/2 ton status

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    throttle bushings can be repaired pretty easily if you can have access to a drill press, can find the brass tubing show below (R/C hobby shop), have an 11/32 drill bit and some green locktite.

    Here's how it looks in my garage..

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]


    the process is pretty straight forward. Disassemble the throttle plate (file away the exposed screw thread completely so you dont break them off in the shaft), setup in a drill press, use a 5/16 rod for alignment (I used 5/16 brass tubing that I bought at the same place I got the 11/32 pictured below), and drill the throttle plate. install the bushing with green locktite and reassemble.

    Be sure to replace the throttle blade screws with new ones and restake them or at least use green (290) locktite on the old ones.


    Cheers!
     
  11. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    That looks cool and easy. Would be neat to do sometime just to have another good carb sitting around /forums/images/graemlins/thumb.gif
     
  12. dendeanda

    dendeanda Registered Member

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    I have an '85 blazer w/ a 350. I recently found out that the q-jet that is in there is not the original one, this one is older. I know this because there are alot of vacuum likes and wires that dont connect to anything. I was told that the previous over probably did this because the original one was more "electric" i guess. The problem I have with this one is that when i go 4-wheeling on steep hills, it sounds like my carb starts to flood. Wy is this?
     
  13. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    The original owner did that because he didn't know better . You need some of that hooked up . A good rebuild kit , check the float level , choke , hook up some of the vacuum hoses , and try it again .

    Mine actually runs better with the hoses hooked up than without . I just run egr , vapor can , and pcv valve .
     
  14. trailblazer86

    trailblazer86 1/2 ton status

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    http://www.73-87.com/7387garage/garage_drivetrain.htm



    Go to this page and scroll down a little and you will find lots about the Quadrajet.
    Tuning rebuilding etc.

    The Quad is a great off road carb. It is a great on-road carb.
    Look at the size of the primary bores. Great throttle response in the woods and good gas mileage if you can keep your boot out of it.
    Some are 750 CFM and some are 800cfm but the vacuum secondary keep it working great on almost any engine 305-454 cid or more.
    Your carb is rebuild able and easily modified.

    P.S.
    The Throttle bore bushing replacement by Florida4X4 is one nice job.
     
  15. wazzabie

    wazzabie 1/2 ton status Premium Member

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    Where did you get the throttle body screws at for the qjet? How are the screws restaked? Are special screws required?
     
  16. anjieandjohn

    anjieandjohn Registered Member

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    Any idea what the part number would be for the sensor on the thermostat housing? I need to replace mine as it has NEVER been changed. I am in the process of doing a little work to make sure my Qjet is adjusted correctly as well as timing and that. Thanks.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Not quite what you are asking, but you might play around with that sensor and see if it's working right.

    I suspect it's actually just a switch that is either open or grounded based on coolant temp, should be pretty easy to test with a multimeter. A lot of this emissions stuff is hard to find and expensive new, (not to mention the questionable quality of many aftermarket parts) if you can test it easily that's what I'd recommend.
     

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