Hey guys,

I need a new stat and don't know which one would be best.
The engine is pretty much stock, with performer intake, thermoquad, true dual exhaust and re-dialed distributor (18 degree initial and 36 total with light spring).
The car is only driven in the summertime and I like to step on it.
It has the original fan with a thermal fan clutch.

I can choose between 195, 180 and 160 F. I always thought the car ran pretty hot, but the old stat could have been damaged for a long time.

I would like to use a cooler stat, because of the advanced timing, but I don't want to damage the engine. and I also like to have the best performance I can get from this not so powerful engine.

PS: Sorry for my bad english. If anything is not understandable, please ask. I will try to explain it in other words.

195

180* is plenty. It allows the engine to run cooler but hot enough to burn off any condensation in the oil. All that will do is make sure it gets to 180 before the water fully circulates. It won't keep the engine from getting any hotter than 180. But a cooler engine runs stronger.

The thermostat only controls the warmup temperature, if the cooling system isn't capable of maintaining that temperature the car will run hotter than the thermostat setting.

IOW, installing a 180° is no guarantee that it won't run hotter than that.

nothing less than 180. EDIT Unless a 1/4 mile dragger, then a 160.

195

I run 160F in my street hot rods, they run hotter than that !

180 is good for street.If its new then most run 195s bevause of computer controls and cleaner emmissions.I run 180 in my 440 and it never goes over 185 190 even when its 90 out.Rocky

The 195 will actually cool better because it allows the water to stay in the radiator longer. Thermal efficiency is 210. Yes they do run stronger when they are cooler but if you are not drag racing, you are just driving and the temp while driving will be above 160 even with the 160 thermostat.

That violates several laws of thermodynamics.



What?

Do you mean that a typical four-stroke engine is most efficient at a coolant temp of 210? If so, why?

True that I'm no expert. Say if you are coasting down a hill and the coolant temp closes the thermostat, the coolant that is locked in the radiator is still cooling from the air flow. You will watch your temp gauge go down. Coolant transfers heat away best at 210. Now I don't know if this is with all liquids at a certain number below their boiling point or not. I do know that with automobiles 210 is thermal efficiency.

Todays aluminum engines may need 210 but our old cast iron blocks operate much better at 180-185*. You need to remember that the thermostat starts opening before the rated temp which indicates full open. In the example you state the coolant sensor is in the engine not the radiator so you wouldn't see any temp drop.

The rated temperature is the start to open.

Agreed. I'm just pointing out that the opposite can also be true. A 160 or running no thermostat doesn't necessarily make things cooler in the long run. Coolant that doesn't stay in the radiator long enough won't get cooled.

The thermostat controls the minimum operating temperature only. Use a high flow thermostat. 60%water 40% coolant and a bottle of wetting agent. Today's gasoline is very different from 1970 and is designed to run in engines running 200-210 degrees.

Thru the use of instrumentation[air-fuel meter] it is observed that when the operating temperature is below 195 degrees raw fuel will collect in the intake at idling & low rpm and burn off at cruise making the a-f rich then lean.

The old iron runs great at 195 - 210. 210 is not hot, 220 is warm 230 is hot.

Lot's of wives wagging their tales here.

OK, we've all heard that....but by that thinking, wouldn't the same coolant not stay in the engine long enough to pick up heat???

I'd run 195, double check the rest of your cooling system to make sure its working right.

Good point Pacnorth! Never really thought of it that way. I guess if the whole system is up to the task it's up to the task at pretty much wherever you want to set it? I have a 195 in my 400 and the temp gauge is right in the middle.

Any9one ever look at the math that calculate heat transfer efficiency?

NO

Of all the variables in that calculation TIME is not one of them.

The primary variable is heat differential.

The higher the difference the better the transfer. So please stop with the time in the block/radiator wives tale.

As for thermostat temps, that is the floor, not the ceiling. Running an engine cool is not a good thing for anything other than a dedicated race car.