Petcock thread size

Heating, Cooling & AC

  1. Knebel

    Knebel Senior Member

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    Are all Petcocks (drain tap) on a 68 plymouth 1/4 inch or what thread do they have? I am trying to figure out how I can install a coolant sensor, I cant get the plugs out of my manifold.... and need the one spot i have for the sensor already in there. So i thought, just remove the petcock and put a sensor in instead.
     
  2. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Should be 1/4 NPT.
     
  3. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    A coolant sensor at the bottom of a radiator will give you an abnormally low reading. Not a good place for one.
     
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  4. 70bigblockdodge

    70bigblockdodge Old Man with a Hat

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    Coolant sensor is usually 1/8 NPT
     
  5. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    [​IMG]
     
  6. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    But let's go back to getting the plugs out.

    What have you tried? I know that a little heat with a torch goes a long way if there is pipe dope on the threads.
     
  7. Knebel

    Knebel Senior Member

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    Well, im under a carport in an apartment, that severely limits me. The one I got out before, to install my sensor, i had to drill out. No heat, no soaking worked....

    So far i have just soaked it in pb blaster for 3 weeks, put the allen wrench in, used a pipe to have more leverage and the thing does not move one bit. Stopped because i didnt want to break the manifold.

    Oh and the lowest i can adjust my thermostat is 150.
     
  8. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    Is this a SB or a BB?
     
  9. jct

    jct Senior Member

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    have you tried hammering on top of the wrench while trying to get the plug out?
     
  10. Knebel

    Knebel Senior Member

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    Yes, tried hammering too. Its hard to get to. It is a sb with an edelbrock performer 318/360 intake.
     
    Last edited: Jul 2, 2016
  11. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    And which one is breaking your ballz?

    PicsArt_07-02-10.10.07.jpg

    What do you currently have in #1, #2, and #3.
    Trying to get a PICTURE of what's going on.
     
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  12. Knebel

    Knebel Senior Member

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    [​IMG]

    I have a sensor for my electric fan thermostat in 2, water temp std sensor in 1. The rest are plugged with allen wrench pipeplugs. If i rip on it like a berserker, id either break the manifold, bend the allen wrench or round out the plug... but it wont move. The one i got out last year, i tried dry ice, heat, soaking it in all kinds of stuff, nothing.
     
    Last edited: Jul 3, 2016
  13. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    PicsArt_07-03-07.49.02.jpg
     
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  14. 65sporty

    65sporty Old Man with a Hat

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    I use a Allen socket with a ratchet, did you drain down the coolant? I will hit the top of the plug with a hammer, use heat, and remove
     
  15. commando1

    commando1 One Sick Puppy FCBO Gold Member

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    Can try welding a bolt to it.
     
  16. livininharrow

    livininharrow Senior Member

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    you are not trying hard enough. a pipe thread fitting will always come out as it is a tapered thread. you should not have to worry about breaking the manifold. more leverage my friend . also heat as mentioned followed with cold water immediately will tend to break the seal in the threads.
     
  17. celticwarlock

    celticwarlock Active Member

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    This thread is a bit old, but might I suggest an Allen ratchet attachment on an impact gun? I have had a lot of success with that combination. Combined with heating/cooling and even without it, it should prove most effective.