[Jacques Reed]

Thanks Lynn, Always glad to contribute to the knowledge base.

As a matter of interest I was pretty certain they were NPT threads on the fitting and not BSP as the origin of the vehicle was North America. I thought I better check anyway as Canada being a Commonwealth country they could be BSP. We all know how many different thread forms are sometimes used on our MV's.

I tried measuring against a 1/8 BSP tap but that was inconclusive as I could only engage about 3 thread due to the first three engagement threads of the tap being reduced height. I then set my Vernier to 5/27" (0.185") NPT size and compared the five threads against it as per photo. Again, inconclusive as 5 BSP threads would be a distance of 0.179". My old eyes cannot distinguish 0.006" difference on an old fitting.

I then remembered the major diameters are different and measured the fitting. Sure enough, the fitting is 0.403 diameter at midpoint of the threads.
I put the Vernier across the BSP tap and it passed through with out even getting close to the sides as the major diameter of 1/8 BSP is 0.383"

Always more than one way to figure something out.

Hope this is of some interest.