Spitfire temp sender for spit 1500

Hi all,trying to fit an aftermarket watertemp sending unit into my'78 Spitfire. The sender is 1/8 NPT, I tried a 3/8 NPT to 1/8NPT reducer but that didn't fit into the waterpump housing. Can anyone tell me the actual size of the holes in the housing. Thanks in advance. "LJ" Long

I thought the sender was at the top of the radiator...

Either way, I wouldn't even bother with it, and would just get the pointy brass through-radiator type that comes with a new electric fan and reroute the wires.

Are you trying to utilize the location in the image above? I'm not sure exactly what the stock thread/hole size is, but it's not NPT and it's very close to 7/16". The original sensor used a washer to seal it. I installed Sun mechanical gauges in my MkI. I used a 1/4 18 NPT tap on the hole without any drilling. It seems to work fine. The brass is what came with the gauge. I hope that helps.

The sender I took out of my 76 is a 5/8" and the thread is 18 pitch.

(It is not NPT)

Well, got it sorted out. The sender is the one that come's with my temp gauge. It's an AutoMeter # ATM-5737. Of course I wouldn't want to replace it with one of those "pointy brass" units as those are primarily just a thermostatic switch for turning a fan on/off. Secondly I was wrong about the size of my sender unit. It's not 3/8 NPT as I stated but 3/8" 27 TPI The opening in the water pump housing is indeed 5/8" as Ross indicated. The obvious thing to do would be to find an appropriate adapter. This has proved to be difficult. The solution it seems is to drill and tap my alloy thermostat cover for the 3/8" sender. I find that this seems to be a common problem when using aftermarket products and hopefully someone can use the info. Thanks to all for their input.

ljlong said:

The solution it seems is to drill and tap my alloy thermostat cover for the 3/8" sender. I find that this seems to be a common problem when using aftermarket products and hopefully someone can use the info. Thanks to all for their input.

Click to expand...

I'm not sure that will work, unless you find a thermostat that will clear the sender. This was a situation with Heralds, but those cars used a 'flat-top' thermostat similar to those found in the TR2/3/4.

The adapter of a 1275 will work just fine on a standard mg mechanical gauge. It is what i used to swap to a dual gauge on my 1500.

Part number 56

https://www.victoriabritish.com/icatalog/sm/full.aspx?Page=54



mark

<span style="font-size: 12pt"><span style="font-weight: bold">YEP</span> this is the part that worked for me on my 1500 spit...</span>