They have several options on their site, which one is correct for our engines?

 

You always want to start with the smallest one, 1/8npt. Not the 1/4npt. That way if you drill/tap too big you can still go to the next size up and not have to weld the thermocouple to the exhaust manifold.

 

I'm alreay tapped for an 1/8. It looked like there were different probe lengths on their site, like 658 or 658s (short)?

 

R658 will work. According to their catalog, says the R658 is only good to 1600*f. Says it is adjustable for depth too. I have the R658HT. Same except for high temp inconel tip to 2000*f. Most Isspro thermocouples are 1/4npt. I *think*, there is a 1/8-1/4 adaptor available. I don't see it in their catalog though.

R658s is for smaller diameter exhaust tubes.

Have you already bought a pyrometer? FWIW, when you buy a pyrometer from *most* vendors, such as Geno's, PDR etc, you get all you need to install that pyrometer in your truck- gauge, lead wire, probe etc. Way back when I kinda got screwed over from a shop. I didn't know any better, told them I wanted all these gauges, got home, and that was all I had.. was gauges... no boost tubing kit, no lead wire, probe for the pyro. They made me pay EXTRA for all that... when you can get it all from *most* online vendors.

 

Yes there is an adapter available...I bought it for installation in my marine Cumins that had a 1/8 fitting already available.
Call or e-mail them and they'll give you the part number.
Jay

 

I believe you are looking for the short thermocouple ....I "think" it's the "K" model but a quick call to PDR will get you "gospel" on that question...


pb...