Thermostat temperature rating question

[chrisntam]

So if a thermostat begins to open at 180 degrees and is fully open at 202 degrees, is it considered a 180 degree thermostat?

Asked another way, are the temp ratings of t-stats based on when they begin to open or are fully open?

The FSM for my '70 says it starts to open around 180 and fully open at 202.  For such a simple thing, this confuses me.

Your thoughts will be highly appreciated.

chris.

["Cadillac Kid" Greg Surfas 15364]

Chris,
That would be a (nominal) 195 degree thermostat.  Just a side note, going to a lower temperature stat will let the engine run cooler during the winter, not exactly desirable, but the motor will still find its own balance point in the Summer here in Texas at about 210-220 degrees.  If they can keep that they are happy and efficient.
Greg Surfas

[TJ Hopland]

I too would say the 180-202 rating would be called a 195 stat.   

On a warming up engine that 180-202 can happen in less than 30 seconds and you will see it fluctuate as the cold water in the radiator suddenly cools the engine but after a minute or two it should settle to around 200 +/- 10 assuming ambient temps are not extremely hot and you are not loading it.    Its kind of interesting to watch with one of those IR guns probing around various points of the engine and cooling system .