Engine/Transmission (1994 - 1998) Pyro Probe Length

[DMC]

I have searched and searched the boards trying to determine the depth of the exaust manifold on a 12 valve motor at the flange, where you are supposed to install the pyro probe for pre turbo temp monitoring.

I recieved an Isspro 650HTS non adjustable probe, and the length of the probe from the bottom of the threads on the pipe fitting is 1 1/2''. The box it came in was for the 658HTS which is adjustable, I guess someone screwed up. I'm thinking this will be to long, and dont want to get in the middle of this job and have to plug the manifold.



Also I was wondering if anyone has succesfully replaced an adapter that was previously seated on the thermocouple. It appears that one could heat up the compression ring and tap the fitting off of the probe.



Thanks



Don

 

[GAmes]

Make it easy on yourself and send it back. The non-adjustable is less expensive, so you didn't get what you paid for.

 

[DMC]

I've thought about that, but since I already had it I figured I would use it if its not going to be to long.



Thanks



Don

 

[Andy Redmond]

Carefully cut the ferulle off with a die grinder, cut off wheel etc. When it almost goes through the brass twist the ferulle loose with small pliers. Find a good hardware store and get some 1/4" brass compression ferulles. Adjust so the probe is inside the manifold/exhaust stream at least a 1/2"



FYI I think they "set" the probe for post turbo use or a non-"B Series" application that has a deeper manifolds than our baby Cummins have. . Isspro gauges are found in many applications.



See isn't it fun to lick the problem! Or GAmes has a point if you don't want the hassle. .



Andy

 

[Joseph Donnelly]

Without actually measuring various points in the manifold, it probably is not over 1. 5" deep. Ideally the probe will extend about 1/2" into the port, definitely not over 1". Sounds like yours is way too long.

 

[DMC]

Thanks for the posts guys. I sent David at Diesel Manor an email yesterday evening explaining the problem I ws having, and he had already sent me another one via UPS. Apparently there was a screw up at Isspro and the R650SHT somehow ended up in a R658SHT box. He said to keep the wrong one. Maybe I'll put in the down pipe later for reading the post turbo temps.



Andy: Thanks for the suggestion about the cut off wheel. I dont see how I could get the top jam nut up high enough to cut the ferrule. I still wonder if a guy could heat the area where the ferrule is and tap the jam nut down with a deep well socket, thus moving the ferrule down far enough to get at it with a cut off tool.



Well I really dont have to deal with it now so I guess I'll just wait on the new probe.



Thanks Again Guys



Don

 

[Andy Redmond]

Don:



I screwed up, you are right. I should have read your post more carefully. I would be hesitant to heat and tap it down. Many worry that the thermocouple will "erode" and fall apart going through the turbo. Most of us have decided the urban legend is worth the risk for more accurate EGT readings. However, we would all feel remorse if it came apart later after our "modification. " Personally I would think it might hurt the accuracy or function of the thermocouple rather than it physically destructing. FYI I have changed a few malfunctioning thermocouples for most all of "favorite" gauge brands.



Okay. . last comentary about four years ago at a "truck meet" in Ft. Worth TX, I observed some fellas installing a pyro pre-turbo. They had drilled/tapped the manifold, but had a torch and a block of wood on the ground. As I looked closer, vise grips were attached to the thermocouple ferrule (that I thought you had) and they were striking the visegrips with a hammer, attempting to press the locked ferrule down further. It must have worked, but I often wonder if the pyro was accurate and if it ever fell apart. The poor ferrule may have had a tough time sealing the exhaust gasses, with the vise grip treatment.



I know Murphy would not have been so kind to me!



Kudos to your great vendor, mistakes happen, but isn't it nice when someone has customer service and makes it right?



Have fun.