I was expecting 37 1/2 hp out of it!  

I'm going to try the housing and sensor first. Thanks for the advice.  Still find the 850 fun for a trailerqueen.

On a 850, temperature gauges are for sissy's.
When it pukes coolant out the overflow, you're overheating. It's not like you can hurt the little thing.

..and congratulations, it looks like you have the fan on the right way.

That is a fancy valve cover for an 850. With that on you could be pumping out 37 hp!

It is available from Australia if the sanding does not work:

//minisport.com.au/mini-forward-facing-thermostat-housinga-with-temp-adaptor

A little expensive perhaps with shipping.

Terry

Russ, I stand corrected. Having not much contact with early 850 stuff, I'm glad to learn new stuff. I guess you would swap out

the head as 850 stuff is available at very low cost here in the states. It's just not popular.

It sounds like I will try the original thermostat housing again, I had tried to sand /flatten the base of the original.   I'll have a go at that again.  I've got a Auto book 1977, Haynes 1986 and Haynes 2003 and none of them appear to address this issue.

Early 850 cyl heads don't have a hole or a boss to drill a hole into. There are several thermostat housings. The one with the hole is for a sender but the angle makes it close to the valve cover. If the one you have fits and lines up try placing a sheet of sand paper on a pane of glass and sand the mounting face till flat. May have to use course paper followed by finer paper. 

Just about any small bore head would improve performance and offer a sender boss with threaded hole. The 295 casting will kill compression unless surfaced almost the max allowed. Steve (CTR)

Drilling & tapping for a sender hole isn't the work of 5-minutes, either in the head or the thermostat housing.

Best look for another housing.

Not all 850s had a temp sender. On early ones in the 60s (and Morris Minors before them) there was no boss for the sender provided in the head.
The thermostat housing with the sender hole was a BMC accessory, sold to address this problem.

temp sender is in head w/ single wire. Look at the engine it's on the right side of the head above the altenator.  Easy to replace. If you're asking this question, you need a Haynes workshop manual.

I'm asking for an orientation to the 850 engine, with respect to using a water temp sensor.  Where is a water temp sensor installed?  On the thermostat housing?  I have a used thermostat housting with a hole I assume was for a sensor, but I was having difficulty getting the thermostat housing to seal, so I purchased a new thermostat housing.  I have a new thermostat housing without a hole for a sensor, can I add a sensor hole to it? Would it be effective?  And any advise as to how/where to drill the hole, if that is th solution?  Or adapt the heater outlet port of the head?   I'm planning to use a Gtr101 sending unit sensor.