Water Temp gauge thread problems...

How would you guys tackle this problem...
The threaded holes on the intake and water pump of my 55 Y Block are all 3/8 pipe thread. The temp sender (mechanical) for my VDO gauge will thread into the holes, but it isn't a snug fit, it will shake around. I don't think I could teflon it to work, either.
I tried to get a tap for the adapter that I have, but the tap was $15, and the drill bit required was a 45/64, not a stocked item, and probably big bucks from an Industrial supply house. Then, I asked about getting a tap that would fit the sender itself, and the guy told me it was a "flare" fitting, not a pipe fitting, so he didn't have one, he said it would be available at a welding supply house.

Should I try to find the tap for the sender itself (not the adapter) and get the drill bit, too?

I thought about just threading it into the hole and JB welding the hell out of it, but then I'd be screwed if I ever needed to remove the intake or the gauge.

How would you proceed with this? I've been using a 3" long adapter with the sender in the cold side of the water pump, and I want to relocate it to the intake for a more accurate reading.

 

hardware store should have flare to pipe adaptors i think.if not maybe a friend with a lathe could make one.

 

The mechanical temp gauges for S-W mechanical gauges take a special fitting and the VDO probably takes the same fitting.
It may be available at a parts house, but I'm not sure.

The reason the temp bulb at the end of the capillary tube is rattling around is that it needs to sit on a step inside the fitting.

If you can't find one, I think I have an extra.
Lemme know....

 

The only way we could make the adaptors work, resulted in this 3" tall deal that I've been using at the water pump. It would screw into the water pump almost sideways, so I was sure it would fill with water. I'm afraid that if I had this 3" donger of an adaptor on top of my intake manifold, water might not circulate by the sender the way it is supposed to, and I was kind of worried that it would water might not even ever make it up into adaptor.

C9, I'm not sure I follow you. I am pretty sure that the hole is a hair wider than the fitting, almost like if you put a metric bolt into a standard hole of almost the same size, if they happened to have the same pitch.

I'll check with NAPA tomorrow, if I have problems, I'll probably check the welding supply shop and drill and tap for the sender threads.

 

The fitting you want is going to be 7/8" across the flats and about 1" high.

You may be able to make one with a brass fitting from a hardware store.
I have drilled out and tapped 3/8 NPT fittings that adapted to a 1/8 NPT.
One of those may give you enough room for the threads plus the required step.
The step is what the angled (flared) upper part of the bulb seals against and the angle/flare is driven down onto the step by the threaded piece on the capillary tube.