I'm just curious, if there is a rule of thumb like, if you have a 195 degree T-stat, and if you go to a 180 degree T-stat, it will run X degrees cooler, etc, or am I looking at how it works wrong? I'm running a 195 degree T-stat and I'm running 210-220 on the road with Water Wetter and water (went to 230-250 when shut off), smallblock radiator though, which is prolly the problem.

I also thought I would throw in, it is a mechanical autometer gauge mounting in the heads (and the line is routed away from headers), and the heads are aluminum. I'm reading in searches that it looks like if you mount the gauge in the heads, it will read a bit (10-20 degree cooler?), and that's a bit normal, and I'm also wondering if the heads being aluminum makes for more heat dissipation and a higher reading too? Just curious, thanks...

Well, I think with a system that is working correctly you shouldn't vary too much from the tstat's opening point. I'd say 10 degrees either way would probably be somewhat normal.

I don't know if putting in a lower rating tstat will actually lower the average temps. Seems like that's a controversial topic.

When I replaced my worn out, original small block A/C rad with a 4 row Copper/Brass, it definately keeps the coolant closer to 180 than my old rad. The old rad would not drop below 190 after getting there. Now it might reach 190 after a lot of idling but quickly drops to 180 or lower when I get moving.

Taylor,
You are only correct if the cooling system is capable of dissipating the additional heat to get the temperature down to 180. The thermostat really only controls the "minimum" temperature that the engine will run at once its warmed up. If the rest of the cooling system is not doing its job, or does not have enough capacity, the engine will not run any cooler.

I'm hoping I can hold out till next summer to replace the radiator. Heat index out right now is 107 degrees, but I hope with the end of August things won't be so hot for so long.

Can anyone tell me if I'm right about the temp sender being in the head, and its readings?

Thanks..

I think the head reads hotter than if in the intake, they all warm up after shut off,you're not circulating coolant any longer and it warms slightly before cooling down.

Does aluminum have a better resistance to cracking during heat than cast iron does?

dont run it that hot!
take the 195 degree thermostat out, and put in a 160. The 195 isnt helping the situation!
Infact i just remove the guts of the thermostat and use it as a restrictor plate.

A running temperature of 180-190 would be fine, i'd like mine to be at about 60 degrees, but we cant always get what we want, now can we :D