Petcock thread size

Knebel

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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.
 
A coolant sensor at the bottom of a radiator will give you an abnormally low reading. Not a good place for one.
 
Coolant sensor is usually 1/8 NPT
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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.
 
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.
 
have you tried hammering on top of the wrench while trying to get the plug out?
 
Yes, tried hammering too. Its hard to get to. It is a sb with an edelbrock performer 318/360 intake.
 
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Yes, tried hammering too. Its hard to get to. It is a sb with an edelbrock performer 318/360 intake.
And which one is breaking your ballz?

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