1g Thread Sizes

[Big Bald]

I have a 90 Water Pipe and Thermostat Housing. I want to know the thread sizes for each of these parts. I believe the one on the Housing is 3/8 but I not 100% sure. The one on the water pipe looks to be the size of 3/8 but that doesn't seem to want to fit. I am thinking it may be a metric size instead. I do not have the original parts that threaded into these holes so I have no idea how to go about find out the sizes.

Thanks.

 

[tsunari]

Kinda old, but deserves an answer none-the-less.

The 'big' ports on a 1g Tstat housing are 3/8" BSPT (close to NPT, but not quite).
The small ports are 1/8" BSPT. Not sure about the water pipe thread . . .I'm still looking for that info.


*****UPDATE*****

Found the thread size/pitch of the 90-style waterpipe bung in another thread, it's M16x1.5