Have a 1973 FE 390 with no thermostat to my suprise.

The aluminum T-stat housing is so
corroded that it will not accept the T-stat.. probably the reason for no thermostat.

Noticed , three temperatures of T-stats are are available:
160F, 180F, 195F.

What would be the criterion for selecting the T-stat temperature?

 

I bought the 180 as that is the temp I want my engine to stay. If it tends to run warm get the 160 and it will open sooner. I have no idea why someone would want to run hotter except maybe in the winter for heat? lol

 

Book calls for 180 and that's what I use. If it overheats you need to find the problem not cover it up.

 

Appears to be little interest in T-stat selection subject.

My take on the T-stat temperature selection is if the engine is used in the tip of Florida or southern Texas then 160F is probably a good choice.

If the engine is started at ambient temperatures at freezing or below freezing believe OEM 195F or higher would be appropriate.

180F T-stat temperature would be good for southern states except for CA mountain areas.

The temperature rating of the T-stat determines the time it takes to open the device based on the ambient temperature and the temperature of the engine when starting. If the engine is at sub freezing temperature the engine will heat up faster with a 195F T-stat compared to a 160F T-stat.

The T-stat does not regulate coolant temperature in the vintage engine.
When the coolant temperature in the engine manifold reaches the temperature setting of the T-stat, the device fully opens. It is either open or closed.

After the T-stat opens the operating coolant temperature is a function of ambient temperature, engine speed, vehicle speed ,load, and radiator condition. There is a wide variation in operating coolant temperature as compared to a modern engine.

Prefer the 180F T-stat because my engine is not started at ambient temperatures below 40F all year round.

 

My 390 runs on the cool side, assuming I can trust the old gauge and sending unit. It takes a while to get the heater going when it's cold. I have a 180, which replaced the existing 195, and I don't see any noticeable difference in summer or winter.