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AC high idle on a non-TBI truck

Discussion in 'The Garage' started by dremu, Sep 15, 2006.

  1. dremu

    dremu Officious Thread Derailer Premium Member

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    All this talk about upping the idle for OBA has me thinking...

    but my truck is a '74, carb, no computer. It had AC, though I've yanked all the stuff off ... and it's a bit of a bastard, '75 style hot-air choke and no idle stop solenoid that a '74 should have.

    Anyway, is there an easy way to engage whatever system this carb uses to up the idle when the AC is on (was there such a system)? Or should I just get a manual choke cable? That might be kinda fun for crawling anyway...

    -- A
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    If your Q-jet has the threaded holes for the solenoid , get a solenoind , and then you can run a switched 12 volt source to it to engage it . Pretty simple in your case :thumb:
     
  3. Rolled

    Rolled 1/2 ton status

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    you could also fab a bracket to hold a solenoid if there are no screw holes for factory bracket. Should be pretty eays. just use a manifold bolt hole or something close to the throttle.

    Junk yards are ull of the solenoids. Home depot has all sorts of hardware to make brackets out of...


    Did they make qjets without ac solenoid provisions?
     
  4. dremu

    dremu Officious Thread Derailer Premium Member

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    I could fab one, yes, but I'm lazy, and would rather use factory stuff if possible.

    Had to look in the factory books, but lo and behold, yes, the M4MC is *supposed* to have an AC solenoid, but mine was stripped off before I got it ... so to the Pick-N-Pull I go, and I'll get hooked up :)

    Thanks all!

    -- A
     
  5. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    The factory one is adjustable for speed too . The plunger end is a hex and you turn it with a 1/2 inch wrench to determine the length of it . A few minutes and someone looking at your tach for ya and your golden :thumb:
     
  6. dremu

    dremu Officious Thread Derailer Premium Member

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    Looking at the tach? Nah, a real man does it by ear :haha:

    Sweet -- didn't know that, thanks. One of these days I gotta sort out the fast idle on my '74, come to think of it.

    Is that solenoid ONLY used for the AC, or is it also used when the engine is cold?

    -- A
     
  7. Rolled

    Rolled 1/2 ton status

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    My QJet has one but it is not for AC (no AC) or cold start. It is for deceleration. I guess it helps the engine by letting it down slowly. it is vac operated so the higher the rpm, the further it goes up. When you let off the idle, it goes down fast but keeps the throttle from slamming back too fast. Seems to run the same to me with or wothout it...


    The cold start is a cam connected to the choke.

    Mine is a 1982 hot air choke quadrajet.
     
  8. dremu

    dremu Officious Thread Derailer Premium Member

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    Vacuum operated? I'm thinking electric solenoid ... how does this vacuum thing work?

    -- A
     
  9. Rolled

    Rolled 1/2 ton status

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    it vworks on vac pressure. It also has some wires that go to it. I think it is dual purpose. Either vac or electric. not sure though...
     
  10. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I would of thought the hot air choke would of been gone by 81 . I have one in the garage , I should run the numbers on it see wht year QJ it is :thumb:
     

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