The Stovebolt Site Forums The Shop Area Engine Shop Threaded tube nut and oil gauge line

I assembled my rebuilt gauge cluster about a year ago. It looks fantastic. After installing it in the truck and looking at it for a few weeks I discovered I had the gauges reversed. The water temp was where oil pressure belonged and amps and fuel were reversed. I do not know what I was thinking when I put it together (blame it on being left handed?) but when I realized what I had done I couldn't face pulling the cluster and taking it all apart just to fix that when I could read the gauge just fine. I finally accepted fixing it. When I removed the oil line I found a piece of the copper tube had snapped off inside. So that finally gets to my question.

How does this thing seal? Is the copper tube expanded inside the brass fitting? How far past the brass does the copper tube need to extend to seal? Is an 1/8" enough or does it need to be pushed all the way home and then tightened up? I am thinking if it doesn't have to go in so far maybe it will not break off and ruin another gauge if I ever have to remove it again.

This was pretty well covered including some nice photos from Denny in this thread https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=755376&page=1 but I cannot tell how far the copper tube needs to extend.

Chuck

whether its right or wrong,Chuck, I usually put the line in the guage and then slide the nut up to it and screw it in. Been doing it that way on several guages over the years and never had a problem.
Lets see what others have to say.

When you do something like switch the guages couldn't you "just kick the cat" as Marty once told me

Alvins got it right, with a new nut and tube just slide the tube in till it bottoms then snug up the nut. These are compression fittings and the end of the nut fits into a taper inside the gauge and is swedged in on the tubing.

DG

...Denny, thats the best darn description I've ever heard. We better write dat one down.

Thanks guys. That's how I did it the first time. Either then, or more likely when I loosened it to remove the line a piece of the copper tube is now stuck in the gauge. Really stuck. I guess if I ever have to remove it again I will take it loose at the block.

The good news is I no longer dread installing and removing the gauge cluster. I am actually getting good at it after 3 times in and out. I read about Alvin and others misadventures in re-doing these old trucks and even though I tell myself I am not going to make that same mistake I seem to end up doing the same things more than once.

Chuck

Don’t know how you got the end of the tubing broken off in the gauge Chuck. If anything when the double compression nut is tightened up it should make the tubing smaller not larger. These are one-way fittings, once it’s made up it is not meant to be removed and used again like a standard compression fitting.
You can see that in this picture and you can see the correct amount of tube that extends beyond the compressed area:
http://www.pbase.com/dennygraham/image/137898151/original

Denny Graham
Sandwich, IL