Terry, Glad my solution could help out. Hope it works as well for you as it has for me. I've had to create quite a few solutions when modernizing my car. I might start posting some more of them if this forum ever gets out of the toilet.

To mtymous

That is a great idea about cutting off the end of the sending unit and retapping.  I bought an aftermarket gauge for my Bugeye and the sending unit was much smaller.  You fixed my problem.

Thanks

Terry C.

PS  I also have Mini's

Yes, it was new to me as well, but the oil temp and coolant temp gauges I recently purchased are all like this.

But you are correct the head end or block end is still 5/8 for the BMC engines.

Terry

That's interesting Terry.  I haven't seen that arrangement before.  Regardless, that setup still uses either a 5/8 UNF or 3/8 NPT thread to screw into the engine/head (3/8 NPT being the larger by a few thousandths and having tapered threads).

The last two mechanical gauges that I bought have been this type:

where the adpater has male threads on both sides.

Terry

Mur. I feel the love. Shall I mention that I assembled the drive shaft on Crazy Mike's LeMons Mini at Thunderhill when you (and Spank) could not? I know you were distracted but a girl in a Bikini is no excuse.

Small bore engines do not need the spacer for a mechanical temperature gauge. I think that was already mentioned in this thread. That means cup cake is wrong on two threads this morning. See also brake servo. 

I suppose it has been a few years, but a mechanical temp gauge from WalMart comes with the spacer.

There are some mechanical gauges that are provided with an adapter that has disimilar threads on each end.

the 5/8 18 for the block, but the cap or cup end is different.

I will have to find the instructions for one of the gauges I purchased recently.

Terry

Just to elaborate on the adapter Larry provided the link to above....  The adapter has 5/8-18 male AND female threads.  It is an adapter used to space the temperature sensor further out.  It is sometimes needed if you have a mechanical temperature gauge where the expansion bulb is long and (as Larry said) the tip bottoms out inside the head casting before going in full depth.

There are a couple of different adaptors depending on the sensor. Here's one that might work for you.

//www.minimania.com/part/11K2846/Adaptor-Temp-Gauge-Adapter--Sprite--Midget

If its a mechanical gauge the sender will bottom out inside against the cylinder, so you'll need an adpator. I'll post a picture after I charge up my camera. The threaded collar in your picture looks to have a coarse thread not fine.

The picture looks like you have a mechanical temperature gauge.  Is that what you have installed or what you want to install? 

For the 5/8-18 tap, use eBay if you are not in a hurry.  Select one that has a shiny, ground finish, not one that looks dark or sandblasted.  There are a couple of places on the car where you will need a 5/8 UNF tap to chase the threads... but not many (oil feed banjo bolt on A-series blocks, brake servo hose tap on an intake manifold, and the temperature sending unit hole in the head).  

While you could HeliCoil the sensor hole, there are issues that make it complicated and undesirable.  I can explain in a later post if you want.

Start by explaining what you have installed now and what you want to install.  Measure the threads on both new and old senders with calipers and tell us what you find.  As MtyMouse said NPT threads are tapered so you may find that one end of an aftermarket sending unit's threads are larger in diameter than the other end.  Measure those near the largest end and tell us what you find.

Well the way I would go about it first would be to find a 5/8UNF tap. I think I picked mine up at Harbor Freight or Northern Tool. It's not the highest quality, but it was perfect for chasing the threads on mine while I was fitting the new unit. It only rarely gets used, so the price was right.

I'm really not too sure what's going on in that picture to be honest. If the PO did goober up the threads, he may have tapped it (intentionally or not) for 3/8NPT. Which will look nearly identical to 5/8UNF to me. I believe all NPT threads are tapered though. Maybe someone with a bit more knowledge than me can correct me if I'm wrong.

Your spark plug threads on a 998 head will be 14mm x 1.25. That means they are about 1/16 inch smaller than a 5/8UNF.

I'm pretty tapped out (pun intended...kinda?) on what I can offer. If it was me, I'd try chasing it with a 5/8UNF first. If that doesn't work, you'll have to figure out what size thread you actually have in there so that you can figure out what helicoil you'll need and all that goes with installing helicoils. Sorry I couldn't add much more tonight. Hopefully that gave you a bit more infor to send you in the right direction.

jon, ask a member who has an actual running mini...

I need to find a tap mine only go up to 1/2. I don't think it's big enough to be 5/8 it's close to the same size as my spark plug hole but different threads?

Well. That is.. interesting. haha. And since taking that picture, you've removed everything and cleaned out the threads? Then you chased the threads with a 5/8UNF tap and the threads weren't right?

Her is a pic of what I have

Image Gallery

When trying to add pictures, there's a few ways.

1) If the pictures are just on your desktop, you can drag and drop them from wherever you have them saved to the green circle/up arrow at the top left of the page when you're typing a comment.

2) If the picture is already uploaded to an online server like Photobucket or Flickr, you can right click the image you want to post, "copy image location" and then on the minimania reply page there is a little button directly under where it says "Paragraph" button. That will open a dialogue box that you can paste the link you copied earlier and it will upload it in line

3) You can use standard code of "["IMG"]www.examplepicturewebsite.com/picturefile["/IMG"]". (But you'll remove all of the quotes. I had to include them here so that you can see the raw code. I use this one most often just because I'm used to typing it, but it accomplishes the same effect as #2.

I think first you really should make sure you kow what threads you have now. As Doug said, 5/8 UNF isn't really all that common. Do you have a tap for 5/8UNF?

That is exactly where i am tryin to but it in the factory position. I am not smart enough to add pictures they just keep showing up blank?