0013

I recently purchased a stock ā€™78 and have noticed that it regularly runs just over 200 while at highway speeds. I have checked out other recommendations; fan clutch, water pump, clean out between radiators, I even flushed the radiator, and everything runs the same. So Iā€™m thinking it is time to change the thermostat ā€“ A friend in my local Corvette club suggested I install a 160. What would be the downside to having the vehicle operate that cool? Any recommendations from those of you who experienced similar in the past?

Cheers

Twin_Turbo

the stat has nothing to do with the max. temp, it only regulates the minimum operating temperature, once it's open it's open and then the rest of the cooling depends on the radiator, shroud & airflow.

1970 Dave

That is not to say the thermostat doesn't need replacing--could be sticking a bit and not opening properly to get the flow necessary for cooling--I would stick with a balanced 180 thermostat--not a huge investment--for a small $ you can know if it is the problem or not

SEMPER FI--1970 Dave

comp

and i drill a 1/16in. hole in them for a bleed

Gator81

Agree w/ Dave and Twinnie.
Unless maybe you've got a 205 stat, which is not what should be in a C3. I believe the stocker is a 195, which you may have, but perhaps the gauge is a little off. The stock gauges are very imprecise.

With my '81, I was shocked to see how much junk was between the A/C condenser and the radiator when I first got it. But you've cleaned that out already. I can tell you that I run a 180 stat, and on a 105 degree day in Utah, running down the highway at 75 mph with the A/C on, my temp never hits 200. Given the imprecision of the gauge, it looks like 180-190. In stoplight traffic with A/C on, it may hit 200, but not over.

As far as cooling systems go, the only real mod to mine is that I'm running a Flow-Kooler aluminum hi-perf pump. I can't say how much better it is than a stock GM pump, but it seems to push coolant with more pressure. I have a nearly-new radiator, and I am a freak about keeping fresh 50/50 mix of Prestone and distilled water in there to prevent any carbonate or phosphate deposits from forming in the radiator.

Anyway, I tried a 160 stat for awhile because it's supposed to offer more power from a cooler intake, but it didn't work for my car. I was always running at 180-190 anyway on hot days, and on cool days my engine smog controls (EGR, electronic carb, etc.) wouldn't work properly at the 160 level. So I went up to the 180 and now all is well.

I've read that running a 160 can hurt your engine due to fuel puddling in the intake rather than evaporating as it should, plus it can kill your fuel economy. I think that all depends on a lot of other factors going on with the engine setup. With a mostly stock engine, I wouldn't go lower than a 180. Just my $.02...

Paul L

The factory stat is a 195. That operating temp is completely normal. Cooler is not necessarily better.

OHSIXX

I installed a high-flow water pump and went from 210 to 170 degrees.

Old Black Chevy

Mine is an '80 model that still had the original hoses. Recently she began running up to 210 degrees which was unusual. I saw a bit of coolant near the water neck. As it turned out, there was a hole in my upper radiator hose so small that it could not be seen from the outside. I only found the pin hole by looking on the inside, of the hose, with a high intensity flashlight. Changed upper and lower hose plus the small hose out of the water pump. All is well.

Old Black Chevy/Travis :flag

Larsson

The last owner of my car installed a 160 thermostat, I didn't know that so I seriously thought that something was wrong with my gauge. After replacing all the fluid and the sender and still having same result, a temp around 160, I changed the thermostat to a 190. Now I'm cruising with a temp of around 200 according to my original gauge.

My problem is that the fan is so bad that I can't stand still and idle without overheating.
So maybe this 6$ thermostat will be a good reason for me too buy electric fans, I've been looking for such a reason for a long time

Gator81

If your cruising temp is OK but you overheat at idle, you might want to check the fan clutch. I replaced mine for this reason. Just a thought. :flag

[edit: added this] Forgot to say, my '81 has the auxiliary electric fan, and it never comes on - no need.

0013

Thanks everyone for the advice. I think I'll start with a 180 thermostat -- seems like a good average; I'll see how the car responds from there.

Cheers