Pyro probe 1/4 or 1/8

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When I installed my EGT probe I drilled my manifold for 1/4 npt but had a 1/8 npt probe.
I jury rigged it with a brass adapter and installed the 1/8 probe. I called Geno's garage and explained my situation and they immediately sent me a 1/4 probe. My question is what is preferable. the 1/4 looks more rugged but the probe is longer. I also don't know if the different metals will cause a problem with different expansion rates if I leave the 1/8 in.
I'm leaning toward replacing the 1/8 with the 1/4 but I wanted to hear some other opinions. I'm sure some of you out there have some. #ad



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Jim

Patriot blue Y2k 5sp Stealth 2500 (markings removed)QC,SLT+,leather, camper,TT,lsd,3. 54,4x4,hd xfer case,Geno's dual gauge,DD IIM's and boost module,ARE lid & bedrug liner, Sony 10 disk cd changer.

 

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If it works, leave it alone.

 

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you should have no problem with dissimilar metals. I have been selling thermocouples for many years. BTW the reaction time between a 1/8" and 1/4" OD thermocouple would be nil. If this was a concern #ad

 

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I would install the 1/4 NPT probe. Its not a good idea to expose brass fittings to the temperatores you will see at the manifold. Even though the exhaust pressure at this point is not excessive for brass fittings, the elevated temperatures will weaken the fitting and it may fail.

 

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Same thing happen to me. I used a brass adapter so far it works fine.



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95,2500,auto,410;2-WD
Gear Vender Overdrive
tst #5

 

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Brass won't melt until you reach about 1650 F. You have other problems to worry about if you let EGT's get that high. However, brass starts to recrystalize at about 880 F, and that's easily reached. As grain growth occurs in metals, ductility increases, and tensile strength decreases. You are weakening that bushing every time you drive your truck! Change to the 1/4" fitting, it will be less prone to breakage in you accidentally bump it.

 

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jwgary,

Thanks for the metalurgist's view... . #ad


I believe my new ISSPRO probe is already mounted in a brass 1/4>1/8 npt reducer. (I'll have to double check this when I get home)

Don't you think the gauge vendors would put it in a steel reducer if brass is not suited to the hot environment of our exhaust manifolds? #ad


Mick2500

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2001 2500 ETH/DEE, QuadCab, 4X4, SB, LSD, 3. 54, SLT+, Sport, Intense Blue PC/Agate, Tow Package, Camper Package, 'DC' Bed Cover, Sliding rear window. Ordered 5/01/00... Cancelled 5/30/00... re-ordered 6/02/00... Cancelled again by DC 6/05/00
Gauges (EGT/Boost) and A-Pillar mount Here, 4" Exhaust, Here.