2nd Gen Non-Engine/Transmission Need help with Thermocouple install

[TrqMonster]

I am having trouble finding a tap for my new thermocouple for an Isspro Pyro part # R658. It looks like it must have to be a 9/16-18. We measured the threads to be 18 but when we measuered the probe threads it came out to some odd number between 1/2 and 9/16. 1/2 is too small and Autozone and Menards only had tap and die kits up to 1/2. Sears has a large kit that starts at 9/16 and goes to 3/4. Does anyone know what size to use?



Also, how many turns should the probe screw down.



Just to let you know I am replacing an Autometer gauge and thermocouple and the bottom part of the Autometer thermocouple broke off in the manifold (not the probe but the threaded part is still in manifold). The threads are too small anyway but there is already a hole there if any of this info makes a difference.



I would appreciate any help I can get at this point.

 

[ndurbin]

Sounds like 13mm maybe since it's not 1/2 or 9/16.



Nathan

 

[rluft]

Mine was not a straight thread, but a pipe thread fitting. I bought a tap when I installed mine and will look for it tonight. I will post again with what I used. Seems like it was 1/4 inch pipe thread.

 

[Steve St.Laurent]

I believe Isspro uses a 1/8" NPT (pipe) thread for all it's thermocouples.

 

[bmoeller]

I believe Isspro uses a 1/8" NPT (pipe) thread for all it's thermocouples.

Mine also came with a bushing for the t-couple to screw into. It is 1/4" NPT.

 

[JLEONARD]

Yup... . I think mine (the bushing) was 1/4 NPT as well. You need a pipe tap.



Jay

 

[TrqMonster]

Sorry for my ignorance, so a 1/4" pipe thread is bigger than 1/4" regular tap? Should I be able to buy this at a hardware store that sells plumbing supplies?



I had to tap new threads in the old thermocouple fitting since it broke off in the manifold and I couldnt get it to back out, so now there is just a bolt there and no thermocouple. I want to try and get the pyro installed tonight actually since new turbo goes on tommorow and I want to watch the EGT's.



I had never done a thermocouple install before so I unbolted the turbo and pulled it out of the way when I was tapping the threads for the "plug" bolt and then tried to make sure to get all the shavings out of the manifold. Is this the best method?

 

[JLEONARD]

so a 1/4" pipe thread is bigger than 1/4" regular tap? Should I be able to buy this at a hardware store that sells plumbing supplies?

1/4 NPT is 18 threads per inch and the OD is a little over 1/2 inch, that's why you thought it might be 9/16 when you first measured it.

You can buy at a plumbing supply store, industrial supply house, Sears, maybe Home Depot (never looked for them there), etc. Take the bushing with you to be sure you get the right tap.

Drill size for a 1/4 NPT is 7/16".

Hope this clears up some of the mud.

Jay

 

[BTighe]

i went to 4 different stores looking for this thing. Ace is the only place that had it. it was like 3 bucks. i greased up the tap when i did mine and it caught a lot of the shavings. drilling and tapping was the easiest part of the pyro install IMO. good luck

 

[john3976]

I got the tap at NAPA auto parts.

 

[Dave M]

Installed my Diprocol gages a few weeks ago. . 1/4 inch NPT pipe thread... used 7/16 inch drill... got both at NAPA. When putting thermocouple in exhaust manifold I first unbolted turbo from manifold and pulled turbo back up to the end of the exhaust manifold mounting studs (thats as far as I could get it) so I could put piece of cardboard (on turbo end) between manifold and turbo to keep shavings out of turbo. Used grease on bit and tap. . worked good to keep most of shavings out of manifold... just kept cleaning the tap. Had to tap way deep on tap threads before the thermocouple threaded collar finally started to bite... . used 3/4 of the tap length .



Oh Yeah... . Don't tap too far! Make sure the thermocouple probe threaded fitting doesn't go in too far but is about flush with the inside wall of the manifold. Thats why I seperated the turbo from the manifold, so I could reach my fingers up in there to feel... I have small fetus sized hands :-laf ... you might use a mirror.



Good luck