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787 Gurus. Temp sensor Question

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Rosie2514

Rosie2514

Active Member
I noticed upon trying to install my temp sensor into my "new" buckshot head that it gets really tight after about 6 or 7 revolutions. It will not go down all the way flush like it did on the old head, and if it will it will be a VERY tight ordeal. What im wondering is if maybe somehow i could configure a TTO temperature sensor to use that same hole for an accurate live temp reading. Any thoughts?
 
Dont believe so Joe, using the old head the temp sensor just screws in like any other normal threads.
 
Was thinking of getting the TTO trail sensor and mounting it above the hole using a similiar size bolt and washer.
 
You it should never bottom out. A tapered during is designed to have about 2 threads of "interference" and that essentially seals the fitting. But you still need Teflon tape or pipe dope.

Sent from my SGH-T889 using Tapatalk
 
I was saying it should be pipe thread or "NPT" National Pipe Thread so, yes tapered.
With the tapered NPT threads if they are not cut deep enough you will only get a few turns in because of the taper. If you confirm the new head is NPT then you can use a NPT tap to cut them deeper and allow the sensor do go in a little further.
 
Thanks Racer, i realize the theory of tapered threads. Does it really matter how far it is screwed in as long as it doesnt leak? lol
 
Yes, it does. Your deforming the threads. When we make parts with an NPT there is a specific depth that the tap needs to go so it mates with the part going into it at the proper depth for the proper thread engagement. It's not like a standard straight threaded hole. I wish I had a dollar for every customer that waddded out an NPT thread on our machines because they insist on making the fittings balls azz tight. Sorry Rosie, that's the machinist shop coming out in me.

Sent from my SGH-T889 using Tapatalk
 
Now if you use plumbers tape don't wrap it too thick. I would think the sensor needs to make contact with the head so it throws a ground signal when it gets hot enough to, right?
 
Well i did not put it in that tight yet lol
I just was getting it started with a socket wrench and noticed how darn tight the thing started to get with still 1/4 of threads left on top.
 
mikidymac said:
I was saying it should be pipe thread or "NPT" National Pipe Thread so, yes tapered.
With the tapered NPT threads if they are not cut deep enough you will only get a few turns in because of the taper. If you confirm the new head is NPT then you can use a NPT tap to cut them deeper and allow the sensor do go in a little further.
Click to expand...

racerxxx said:
Yes, it does. Your deforming the threads. When we make parts with an NPT there is a specific depth that the tap needs to go so it mates with the part going into it at the proper depth for the proper thread engagement. It's not like a standard straight threaded hole. I wish I had a dollar for every customer that waddded out an NPT thread on our machines because they insist on making the fittings balls azz tight. Sorry Rosie, that's the machinist shop coming out in me.

Sent from my SGH-T889 using Tapatalk
Click to expand...

Matt Braley said:
Now if you use plumbers tape don't wrap it too thick. I would think the sensor needs to make contact with the head so it throws a ground signal when it gets hot enough to, right?
Click to expand...

These are conflicting whether it should go all the way to the bottom of the sensor or just tighten down lol. You all are trust worthy sources
 
Ironically I was just working on some parts with 1/8 -27 npt taps I use a gauge to determine the depth of tap cut and the fitting tends to stop and get tight with the taper at that specific depth. We never bottom out pipe taps just snug them up with the proper sealant or tape as racer said you will destroy the thread!
262.jpg
263.jpg

As you can see the threads at the top of fitting are still visible.


Sent from my iPhone using Tapatalk
 
Agreed, pipe threads should not bottom out. My guess is that your stock head threads were just cut a litter deeper than your aftermarket head allowing the sensor to thread in a little further.
 
Or someone just went to town on them before i got my hands on it lol Does anyone have a pic of their temp sensor in their head? just to get an idea?
 
Rosie2514 said:
Or someone just went to town on them before i got my hands on it lol Does anyone have a pic of their temp sensor in their head? just to get an idea?
Click to expand...

I have a '96 XP in the shop with a stock head I need to pull off to get some pictures of freeze damage, I'll get you a pic of the sensor in that head in a few minutes.

On Edit:
Ok, here's the '96 XP top view:
266.jpg


'96 XP bottom:
267.jpg


And a '97 to compare to, I know the history & owner's of these since day one and nothings been apart on the top ends yet.
268.jpg
 
Last edited by a moderator:
Rosie, I am interested in how/if you mount a TTO and how it works out for you.

Keep us in the loop.
 
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