[PETE_SIXTY4]

I previously had a 160 degree thermostat in my SBC. The aftermarket gauge would climb to 190, then rapidly go down to 160 before climbing again. I have a 3x aluminum radiator. I mistakenly assumed I had a 190-195 thermostat because that’s what the gauge said when it began to drop. I’m an idiot and didn’t look at the old one until after I installed a new one. I installed a 195 degree one and have let my gauge climb to 205 before shutting it off out of fear of overheating. I’m at a bit of a loss as I’m not sure how well correlated the temp in my gauge should be to what’s going on with my thermostat. Can anyone give me some advise on how to move forward?

 

[japete92]

The thermo 'rating' is the temp it begins to open. By the time it is fully open, the coolant gets a little higher. From your description, everything appears normal to me (with either thermostat/gauge).

I would not fear overheating if you are using a 50/50 coolant mix and running at about 15 psi. In those conditions, the coolant does not begin to 'boil' until around 265 F. It retains its heat transfer capabilities as long as it a liquid.

Moving forward? Because I'm lazy, I'd see what temp the 190f thermo 'maxes' out (at idle). Likely somewhere under 210f. That would not bother me, nor cause me to re-work anything. IF the 'max' was 225f, I'd replace the thermostat because it is likely faulty (even though new). At that point I'd likely go back to the 160f part.

While moving at forward speed, I expect the thermostat to maintain coolant temp close to its rated temp. If it did not, I'd start looking for the reason (it may not be the thermostat).

I'm a fan of the 180f thermostat (especially w/iron cylinder heads). With aluminum heads? 190F. BUT I would not change a fully functional thermostat (160f, 180f, 190f). Like I said, I'm lazy and don't like to futz with 'working stuff'.

The GM 'idiot light' did not glow red until around 240F.

Pete

 

[hydro462]

Use the 160 Stant Super Stat. They are by far the best thermostats out there..

 

[DUTCH MAX HEADWORK]

Stant Super Stats are great. But I prefer 180-degree temp which should end up running inthe190-195 temp if your cooling system is up to the task.

A running coolant temp just above 180 is the goal to extend engine longevity. It's above 180 where you want your oil temp. A160 stat will usually get you there as oil runs hotter than coolant temp, but a 180 guarantees it and gets you there faster in cool climates.

 

[davewho1]

Use the 160 Stant Super Stat. They are by far the best thermostats out there..

What is your reasoning for that statement? Not accusatory, just curious. ;-)

 

[oldcutlass]

Stant Super Stats are great. But I prefer 180-degree temp which should end up running inthe190-195 temp if your cooling system is up to the task...

In addition if you run your car on cold days, a 160 will barely get you heat inside the passenger compartment. A 180 will keep you toasty.