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what's this thingey do??

Discussion in 'The Garage' started by 78Suburban, Sep 8, 2005.

  1. 78Suburban

    78Suburban 1/2 ton status

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    [​IMG]

    my old '66 didn't have this fitting on top of the t-stat housing.. whats it for? 1)there's a line running into the carb, 2) a line running into the vaccume advance on the distributor, and 3) line just laying there with some sort of broken plastic fitting and piece of rubber hose...
     
  2. dremu

    dremu Officious Thread Derailer Premium Member

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    Well, it switches vacuum, liek a solenoid, based on water temperature. I'd guess it advances the dizzie more or less based on whether the engine is warm?

    -- A
     
  3. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    its a temperature operated vacuum switch. ive only seen it on the 81 and newer trucks, but not all of them either.
     
  4. RaisedK5

    RaisedK5 1/2 ton status

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    Its some sort of thermostatic switch. If its attached to the spark advance its probably like my 69 buick. At normal temp it supplies ported vacuum to the dist. at high temps it supplies full manifold vacuum to the dist at idle. the theory is (at least on my 69) at idle, full manifold vacuum will pull higher advance and raise the rpm of the motor thus spinning the fan faster to cool off the engine.
     
  5. 78Suburban

    78Suburban 1/2 ton status

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    what about the 3rd little line with the plastic fitting and piece of broken rubber hose, what's that?

    should I just take that pos of there and get a regular t stat housing? I've been seriously considering putting on my old edelbrok manifold and carb on there anyway.. might could kill 2 birds with 1 stone :rolleyes:
     
  6. 1979jimmy350

    1979jimmy350 1/2 ton status

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    it might also feed your EGR valve so it will only open up after the engine has warmed up
     
  7. az-k5

    az-k5 1/2 ton status

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    I have that on my 79. only it has 6 little vacume hoses on it. (I counted)
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The proper name of that is a thermal vacuum switch. Those are used for various different things such as distributor vacuum delay, egr vacuum delay EFE valve and other things like that. Get a book that covers your year vehicle and look under emissions items and you might find a schematic on it, also usually under the hood or on the radiator support there will be a vacuum diagram if nobody has already removed it or it hasn't deteriorated.
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Your upper radiator hose is starting to split . Don't overtighten the next one .
     
  10. 78Suburban

    78Suburban 1/2 ton status

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    what if I take it off and just run a hose from the carb to the distributor.. would this be ok? I am by no means trying to be emmisions compliant.
     
  11. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Trace them down. If you have a 700R4 it can also be used to keep the torque converter locked up until the motor reaches operating temperature.
     

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