What size tap for EGT thermocouple?

[wscott]

I have been looking at Geno's and their gauges. The gauges for the EGT have two options for the thermocouple. You can get either 1/8" or 1/4" NPT. Any suggestions????

 

[David Muench]

I went with 1/8". . The smaller the hole in the exhaust manifold, the better as far as I'm concerned.

 

[BarryG]

I also would use the 1/8npt then if by chance it gets screwed up you can always redo with a 1/4 and use a reducing bushing. Not likely but a possibility. I would also check to make sure your probe is 1/8 some are 1/4.

 

[jhurst]

I second what BarryG said.



Justin H

 

[jelag]

You might consider this.....



Cast iron doesn't accept fine threads very well..... The gray iron material more flakes, instead of being cut by a tap... ..... that's why you don't see many 1/8" NPT holes in cast iron... .



If you look at the 1/8" NPT and the 1/4" NPT you will see that the 1/8" NPT is 32 TPI (threads per inch) and this is a guess, I didn't get a gauge out and test it..... the 1/4" NPT is 16 TPI as I can remember... . If I have my numbers wrong someone speak up.....



The jest of this is that 1/4" NPT with the courser threads will hold better in gray iron... .



Just my thoughts on this... ...



Jim

 

[bmoeller]

1/8 npt - there are 2 sizes that I know of. 27 tpi and 28tpi. Grease fittings are 27tpi. My gauge came as 1/8, but came with a 1/4 adapter. I used the 1/4 adapter when I installed mine.

 

[Crazy Horse]

I did screw my 1/8" up and wound up going to a 1/4". . . Start small.