The temp gauge on Blue hasn't ever done a whole lot of indicatin'. It does move sort of, to almost around 160 or so when fully warmed up. Maybe there's sludge on the business end of the sender. One thing it does do, is get people to pay attention to the cooling system, replacing thermostats, flushing and replacing hoses, etc to get the gage to read correctly, so that's good.

With the vintage stuff he careful - DON'T install a 16 pound radiator cap on the old iron. 4 to 7 pound caps were used back then. The old radiator is not going to handle that well. A tired engine with a lot of miles, the head gaskets may not either. A 50/50 glycol/water mix is about right for most places. It not only raises the boiling point but extends the freeze point considerable. For some reason straight antifreeze needs to diluted with water to provide good freeze protection to well below zero.

Anybody that solves the Great Temp Gauge Mystery will be a hero, though.

 

If you are using the Ford recommended radiator cap (7psi?) and it does not barf when shut off after a good run it is not too hot.
Eric

 

I pulled the 180 degree out today and replaced it with a 160 degree I picked up at the local Napa. With the 160, the temp gauge reads between 180 and 190, so I feel a lot better and it doesn't seem as hot. I don't have a thermal gun, but prior to the switch the engine was radiating heat so I knew it was too hot with the 180.

It has the stock radiator cap, and it's not 'puking.' That's still the top end of the gauge, so the investigation continues. Do they make any that are lower degrees or is 160 the bottom end?

 

If it wasn't boiling over, then it wasn't too hot. If you didn't measure the temperature then you don't really know anything, other than the fact that the temperature dropped from one thing to another, based on the questionable gauge in the truck. Maybe it did drop from hotter than it should be to perfect, but it also could have dropped from perfect to colder than it should be. You're in Washington and I'm sure a 160 stat is too cold.

If you still have the old thermostat, put it in a pot of boiling water or use a heat gun to open it up. Since replacing the thermostat seems to have dropped the temperature, my thought is that the thermostat wasn't opening all the way, restricting flow through the radiator, causing the engine to run hotter than normal. If you've already thrown it away, I would get a new 180 and see what happens.

Mine operates at about 190 - 200 with a 180 thermostat, in Atlanta summers and if I get stuck in traffic it will climb higher but it has never overheated. So yours should be absolutely fine with 180 in Washington, if everything is functioning properly.

160 is about as cold as thermostats get but it is too cold. You do not want to go lower. Don't band-aid it with lower temp thermostats. Find the problem and fix it. Acquire, buy, borrow the tools so you can do this. And if it is actually running at 180/190 as indicated by the gauge (probably 195-205 actual) now, that is about perfect and is not too hot but you probably do have some problem if it requires a 160 degree thermostat to achieve that.

 

Did you know your engine can overheat without a thermostat? I have seen this numerous times, this is what happens.

In certain cases the coolant moves continually through the radiator without the benefit of cooling and builds up heat. It moves faster than it can be cooled thus overheating the engine. I have seen this happen in vehicles that have larger radiators when pulling a load. Some even overheat without a load just driving at freeway speeds. When they get hot they puke out the coolant. These were fleet trucks that had regular maintenance until some genius started omitting the thermostats.

After they figured that out all engines were equipped with 180's.

Note: my 64 390 in my Bird likes to run around 190 in fact I run 190's in it all the time. FE's like to run warm (but not hot) I have run the Bird like that for 44 years and never overheats even if the outside temp is well over 100. The engine is not quite stock when I rebuilt it years ago I installed a CJ cam and HI Per lifters with other mods to the heads (air flow, etc). I have driven it well over 40K miles with no problems.
Hope that helps.