TR6 TR6 oil sending unit thread size help please?

[ichthos]

It's a long story, but basically I think the PO overtightened the oil sending unit and cracked a some of the surrounding colar on the engine block.I was able to carefully grind this area down and stil make enough room for the sending unit to go in. Now I need to run a tap through the oil sending unit hole. I have a few questions I am hoping you can help me out with. 1)Can someone tell me what type and size of tap I need? Do we have a supporting vendor that carries these, or can hyou tell me where I can get one? 3)Do you need to put anything on the threads before putting the sending unit in? How tight does it sending unit need to be? Any help would on any of these questions would greatly be appreciated.
Kevin

 

[DNK]

Kevin, carries the sending unit or the tap?
Kevin, had this long message typed out then I realized I was thinking the wrong part.
TRF has it and you should call BPNW just to see. It would be at your door tomorrow.

 

[TR3driver]

I'm fairly certain those threads are just 1/8" NPT. You can pick up a 1/8 NPT tap almost anywhere that sells tools (Sears, HF, etc.). Which sending unit you need depends on whether your car still has the anti-runon solenoid; but both are readily available from the usual suspects.

But if you've opened up the hole at all, you may need to drill & tap to the next larger size and use a bushing.

Normally, I would suggest "PTFE Pipe paste" for the threads. https://www.amazon.com/Teflon-Pipe-Paste-4-oz/dp/B000FPDL7O
But if you are having trouble getting them to seal, Loctite makes a product specifically for pipe threads that seems to work better https://www.amazon.com/Loctite-Thread-Sealant-Controlled-Strength/dp/B0002KKTGS

 

[martx-5]

Randall, any chance those threads are British Standard Pipe...

1/8"-28 instead of 1/8"-27.

It seems that most of the world outside of the US using pipe threads follows the British sizes. The oil sending unit on my Miata has the British size 1/8"-28...

Best to confirm the thread count before re-tapping anything.

 

[poolboy]

I kinda doubt it, Art. The last oil pressure sensor that I replaced on my 73 TR6 came from NAPA and had domestic applications.
I agree, though, that it sure doesn't hurt to confirm it.

 

[TR3driver]

The oil pressure light sender for my Stag was definitely NPT instead of BSPT; and I'm reasonably certain the TR6 takes the same sender. At least the one I got from TRF screwed right in and sealed fine.

 

[ichthos]

This is all quite confusing. How do I confirm what type of threads they are? Is the BSPT the designation for British pipe threads? If so, they have them on Ebay. The threads are so close, between 27 and 28, that counting them will not help. I found some of my old notes that say that they are British pipe threads - 1/8" x 28. I forgot I got this information from a British mechanic a while back. What I am going to try first is to locate the tap, and extend the threads into the block. I ordered some of the loctite too.Thanks, Kevin

 

[Rhodyspit75]

If there are enough threads left in the block I would go to the local hardware and pick up a 1/8in nipple and a 1/8in coupling. If your sender threads into the coupling then you know the sender is 1/8in NPT. Then check the threads in the block with the nipple and confirm that they are 1/8in NPT.
The threads on my 75 Spitfire were 1/8in NPT I found this out when I added a nipple and tee for an oil pressure gauge.

 

[ichthos]

I will try fitting it into a 1/8" x 27 NPT at the hardware and let you know what happens. Thanks, Kevin

 

[TR3driver]

Is the BSPT the designation for British pipe threads?

Yes. British Standard Pipe Tapered.
The British standard actually covers both tapered and parallel threads, so there is some confusion over which variety "BSP" refers to. But it seems to usually refer to the parallel version.

 

[ichthos]

Well, the sending unit didn't seem to fit a NPT 1/8 x 27 at the hardware store. Of course I have nothing to check it with to see how it fits into a British pipe thread 1/8 x 28 either. I think what I am going to do it get the British tap, drill and tap a hole, and then try screwing in the sending unit to be sure. I may have to use a nipple and coupler anyway. Any one know what size drill is needed to run either tap?
Kevin

 

[TR3driver]

I just pulled a brand new OP sender, GPS117 (fits TR5-8, Spit 1-5, GT6 1 & 2; except for cars with anti-runon) out of the bin. Using a 10x loupe and a thread gauge, it is definitely 27 tpi, not 28.

If you want to verify, get your own loupe & thread gauge . They are handy things to have around anyway.

 

[hondo402000]

FWIW I purchased a brass T from Lowes and it screwed right into the block 1/8 inch, so I could put the oil pressure switch on one side and another switch that would cut the electric fuel pump on when the oil pressure hit 5 psi and when I shut the engine down the fuel pump would cut off and not run when I had the ign switch in the ACC position

Hondo