2nd Gen Non-Engine/Transmission Thermocouple NPT question?

[litespeed]

I was reading several posts last week via the search function. Now I cannot find them.



I need some help.



I'm about to install my Isspro Pyrometer. The kit I recieved has a smaller fitting to go into the maifold... . I'm assuming I use the smaller one and not the larger one?



What size are these fittings and what thread? I need to buy the drill bit and the tap.



I'm assuming the one on the left is 1/8" and the one on the right is 1/4"?



What size drill bit should I use for either? And which one should I use?



Does it matter where I buy the tools? I dont want to break anything!



I read all this days ago and now I cannot find the info. (now that I need it).



I got this kit from Geno's. No instructions for anything accept how to hook up the gauge wiring to the box.



I have read TST's installation instructions. I know where to put it. I just need to know what I have so I can get the tools to install it.



Thanks,



AJ

 

[BigPapa]

AJ,



You can buy the tools anywhere, just remember, to a point you get what you pay for.



I would suggest using the 1/8" NPT fitting, which is the smaller one. When you buy your tap it will have a drill size on it or they will have a chart listing the drill sizes to use. I think it is 5/16" but don't take that to the bank.



Locate where you want your hole and get a center punch, the one with the sharp point, and put you a little punch mark there with the punch and a hammer to keep the bit centered until it starts cutting. You would do well to get you some cutting oil, you can get it where you get your tap, and use it on the bit until you get down about 3/16" deep. Then start the truck up and let it run while you finish the hole. This will help blow any shavings out. I also dipped the bit in some heavy grease to hold the shavings instead of letting them fall.



Once you have the hole drilled, dip your tap in the grease and cut the threads. Turn the tap one turn then back it up about a half turn. Continue this until the hole is completely threaded, removing the tap and dipping it in the grease 2 or 3 times.



I put a light wrap of teflon tape on my fitting and screwed it in. Remember your screwing a hollow brass fitting into a cast iron hole so don't over-tighten or you'll break it off. Insert the thermocouple to the proper depth and snug the nut up and your done.



It's a simple job and pretty hard to mess it up. Good luck!



Scott

 

[litespeed]

Scott,



Thanks!!



That is what I figured. But I wanted to be sure.



On the TST site it talks about a 1/8" NPT and a 5/16" drill bit. So I assume that this is the bit for this size tap. I guess I'll find out when I go to the tool store.



Are you tapping the hole with the engine running? Or is that just to finish drilling the hole. Good idea...



AJ

 

[SSchang]

I bought an extendable magnet from Sears. It's jut the right size to fit through the hole you drill & tap. Use it to get all the chips out of the exhaust manifold. After I did that, I duct taped the tailpipe shut & started the truck for a couple seconds - it will blow any residual chips out the hole you drilled.



I don't know if I used the wrong size drill bit, but I couldn't tap all the way through the manifold wall. I was afraid I was going to break the tap. I still got several turns of the fitting into the manifold. 45,000 miles later, it still works fine.



Scott

 

[HPetrat]

AJ,

The correct tap drill for a 1/8" NPT tap is an "R" (. 0. 3390") drill.

A 5/16" drill work, but, I would suggest using great care so as not to break the tap.

Also use a grease type cutting paste, it will produce a much cleaner thread in the cast iron and helps to prevent chips/shavings from finding their way into the manifold.

Good luck with the install ,

HP.

 

[AWay]

When I got my 1/8 NPT tap it called for a Q or 21/64 bit.

 

[The patriot]

My taps say right on the tap itself what size drill bit it uses.

Eric

 

[ILIANBG]

It is a size R bit and tap, I think equivalent of 21/64". I would also think it would be difficult to keep the drill straight and steady with the engine on- shaking and rattling. I wonder how you guys do it, do do clamp your drill with drill press attachment?

 

[BigPapa]

Good point Scott, (SSchang). I forgot to mention the magnet and fishing for more shavings. This did yield quite a few shavings after it was all said and done.



I did not leave the engine running while I tapped the hole. The grease held most of the shavings and the magnet got the rest.



Scott

 

[KMott]

I just installed an isspro kit in my truck yesterday. I removed the 4 nuts holding the turbo on and pushed it back out of the way as far as everyhthing would flex. It was a lot of work to get it off, but i didnt want to risk getting chips in everything. I centrepunched the hole, drilled it to 8. 5 mm (happened to have one) which is very close to an "R" drill a lot closer than 5/16. When you tap it make sure you dont take the tap too far as NPT threads are tapered, and it can become too loose.

I stuffed a rag up in the manifold and in the turbo and when all was done i sucked all the chips out with the vacuum. Not sure if it was necessary, but thats what the instructions were that came with the set, so i spent the time.

Goodluck!

 

[litespeed]

A little confused?

Ok, I'm a little confused now... .



Your saying not to tap all the way through the manifold?



If your not tapping all the way through. How far are you going?



4 or 5 or more threads?



I thought the NPT fitting had to be flush with the bottom of the inside of the manifold?



So just getting it in 1/2 way or less is good enough?



Thanks for the help!



AJ

 

[master1578]

Here ya go. .



http://www.piersdiesel.com/TechPyroInstall.htm

 

[litespeed]

Here ya go. .



http://www.piersdiesel.com/TechPyroInstall.htm

Brian,



Thanks. I have already referanced that page. That is just like TST's page that I mentioned above.



http://www.tstproducts.com/pdffiles/instpy25b.pdf



Apparently, Some people are not going all the way through. I'm just making sure so I dont make the mistake of going too far or breaking something.



I damn sure dont want to break off a tap in the manifold.



Funny thing. Piersdiesel says to use an 11/32 drill bit for the 1/8 NPT. And TST says to use a 5/16 for the same 1/8 NPT?



AJ

 

[BigEasy]

Be careful to not tap too deep... I almost did, but I lucked out and had one thread left showing above the manifold. That taper can be hard to judge... do it in a few smaller shots.

 

[HPetrat]

AJ,

As not everyone has access to letter drills ("R" drill is . 339"), a common field practice is to use the closest fractional drill bit. In this case a 5/16" drill is . 3125", slightly undersize (21/64" would be closer at . 3281") and a 11/32" is . 3473", slightly oversize.

If I do not have the correct drill on hand, I usually use a drill bit that is as close as possible on the undersize side of the correct size.



Common practice with an NPT tap is to run the tap in until there are about 6 threads left showing on the tap, remove the tap and trial your fitting.

You should have 2 - 2 1/2 threads engagement of the fitting and then require a wrench to carefully tighten, if not, re-install the tap and thread a little deeper until you have the correct engagement (you don't want to bottom the threads of the male fitting as you may not get a proper seal, ending-up with a leak at the fitting).

This is a good practice to use with every NPT installation as every male fitting may vary slightly from one manufacturer to another (even within the same manufacturers products).



Hope this long post doesn't confuse the issue, but helps clarify :-laf ,

HP

 

[litespeed]

Thanks Big Easy and HP.....



I just got back from the hardware store.



They had a 1/8 NPT 27 thread tap. On the tap it lists a 21/64 bit. I guess that clears it up.



Thanks to ALL for the help!! Greatly appreciated!



I'm guessing I should mark the tap and only go in as far as the depth of the hole and no deeper. It makes since that the compression fitting would bottom out before reaching the bottom... .



Clarity... .



Regards,



AJ

 

[litespeed]

How deep should thermocouple be?

Thanks to all for the help.



I drilled the manifold (engine running). Piece of cake! I tapped the hole (used lots of grease). Piece of cake.



I counted threads to get an approximate depth for threading the fitting into the manifold. I'm pretty sure it is flush with the inside of the manifold.



Now... ... Exactly how deep should the thermocouple be stuck into the manifold? Is 1/2" past the bottom of the inside of the manifold enough? Or is it too much?



I need to know before I tighten it.



It is raining again (thanks Alberto!). So I could not get much done.



I was an aircraft mechanic for 10 years. I have worked on thermocouples on jet engines but never on a truck. I dont like doing stuff half assed.



Thanks again,



AJ

 

[litespeed]

Finished... .



Thanks for the help... .



Works like a champ... ...



Bad focus... ...



Oh well... ... .



AJ

 

[Black Cloud]

The pyro tip should go into the manifold anywhere from . 300 to . 700 flush from the manifold. Great job with your install.