Masfel74

Hello everybody!
I have to chanhe the thermostat on my car (1969 427 L36), which open temperature do you suggest? 160 or 180 °?

Thanks a lot

resdoggie

180*

sfrank2886

sambrand

pro tip, boil the brand new thermostat on the stove to ensure it works, have had a couple over the years that were sticky from the box.

lars

I agree with all above. 180, and check it in boiling water to make sure it opens before you install it. Also, keep in mind that the thermostat cannot control the maximum temperature of the engine - it can only control the minimum temperature. So if your engine operates at temperatures above 190, it's completely irrelevant whether you use a 160 or a 180. But the 180 will assure that your oil comes up to temp and that your heater will work on a cold day.

Lars

mrvette

Many years ago, when buying tstats I noted the 190 stats had a much narrower flow opening than the 180/160 variety......had nothing to do with the opening temp....but restricting flow....of course...

today, last I seen, they all had the same opening neck diameter...so engines run 190+ regardless of when the stat opens.....

SO, here in Florida, I either drill holes in the skirt of the stat, or just easier to trim off some of the skirt bypassing the stat entirely, engine warms up slower, but in hotter climates, so what??

Jebbysan

This explanation should be required in every thermostat thread..........bravo.

Jebby

resdoggie

But its not totally correct. A thermostat is used to maintain a set temperature as well as provide quicker warm up. If your coolant temperature starts rising well beyond your ts temp rating, then you do not have enough radiator. Putting a larger radiator in will increase coolant capacity, provide more available cooler coolant to re-enter the block and thus reduce coolant temperatures. That is how heating/cooling systems work when properly designed. Lots of members in here will attest to that fact because they needed to install larger capacity rads to cope with their increased power and resultant cooling demands to avoid the temps from rising well beyond the ts rating by not changing the rad. Simple thermodynamics - to reject more heat, use a bigger heat exchanger.

Jebbysan

It is totally correct:
"Also, keep in mind that the thermostat cannot control the maximum temperature of the engine - it can only control the minimum temperature."
Stating this.....includes your fact that you need more heat exchanger to cool more heat......a thermostat does not do squat after it is open. That is if you were talking about Lars' post......it is hard to tag a conversation sometimes

Jebby

resdoggie

Lars' statement is false but believed by many. The ts will only fully open and stay open when the coolant entering the block hasn't cooled enough to reduce the block coolant temp exiting at the ts. A precarious situation to be in because now the coolant temperature is dictated by the ambient air temperature. As ambient increases so will the coolant temp entering the block eventually leading to overheating and engine failure if not corrected. Car makers design engines to run at a certain normal operating temp for the conditions expected by the end user and the way they achieve this is to install a ts. Read a GM service manual and see what they have to say about the purpose of a ts. It's not just about quicker warm up.

Jebbysan

But we agree that a thermostat has no benefit in cooling and engine....only maintaining a pre-determined temperature......right? That is where most people get it wrong.
After the engine reaches the opening of the thermostat.....it is solely on the cooling system and ambient to control the temp of the engine.

Jebby

The13Bats

Now argue the misnomer that no stat will allow coolant to flow too quickly and overheating will result.

Jebbysan

resdoggie

The ts controls the engine temperature to whatever the ts rating is by correcting the offset. The engine heat from combustion is transferred to the coolant in engine and the rad rejects this heat and it's controlled by this device we call a ts because that is what ts's do or it wouldn't be called a ts! A ts is a proportional controller and not a 'bang-bang' controller. It responds to correct the error from its setpoint i.e. rating. So for example, this error is seen when the engine load increases, the engine coolant gets hotter which is the offset, the ts which is a control valve that modulates, opens more to allow more cooler coolant from the radiator to enter the block and thus reduce the block coolant temp which is correcting the offset and thereby reduce the opening of the ts valve. If the engines load decreases like going down a hill, the ts valve will close a bit to restrict flow from the rad into the engine to maintain the ts setpoint or close to it. A 180* ts will maintain that temp or very close to that temp but not dozens of degrees above it. Same for a 160*F provided you have the rad capacity. You could probably go even lower than this but the radiator would become too large to fit in there.

I don't think folks understand how a wax pellet ts works and thus confusion ensues and misconceptions are presented. A ts will not be fully open at its rated temp. I'm not making this **** up. For those who care to learn about automotive cooling systems and how they work, here is some reading below. The article, pdf file, written by the guys with the Ph.D's on cooling systems is pretty interesting because it compares 4 different types of coolant systems to decrease warm-up mainly but also normal operating temps thereafter. And the other one describes how a wax pellet type ts works which jives with the results from the Ph.D guys. If I recall, the Ph.D guys stated that the pellet ts was only allowing 42% of the available flow to maintain the normal operating temp - steady state, steady flow. Not fully open is it!

http://vr-12.com/wax-thermostatic-element/

And when conditions are right, you can over heat the engine without a ts installed but wouldn't had you had a ts. But do research to find out why because some folks still think I'm full of bs after repeated posts and references on how our cooling system functions.

Jebbysan

The13Bats

BB2B

I run a 160 in mine. never over heats, never gets hot.

DUB

You wrote and I am correcting it

"if your car runs 220 with a 195 thermostat, putting a 160 in it will NOT achieve squat. It will still run 220.
All of the stuff you explained is relevant, but irrelevant to the average joe....he still thinks cooling is a function of the thermostat.....
A standard stat is not fully open at its specified temp....but about 10 degrees higher is certainly is....especially so for the high flow Thompson/Stant style.
We are both saying the same thing....just different ways to skin the cat."

I have to agree due to I have had customers force me to install a 160 degree thermostat only to realize that is did NOTHING ...like I told them it was going to do. the engine still ran as hot as it did. The only difference was the thermostat opened sooner.

I do agree that from what have been told by guy who was in the automotive cooling industry...a thermostat is fully open 15 degrees above what it is rated at. So I go by that. Whether it is 100% fact. I do not know nor care due to if it is fully open 12 degrees above it rating I am not sweating a few degrees. And the way things are beign made now-a-days we have to wonder if the quality control is that precise.

As written in the pdf 'resdoggie ' provided it states: In particular, the main function of the thermostat valve (Wanbsganss, 1999) is to control coolant flow to the radiator. And as we all know this type of thermostat we are talking about is not an electronic type so it has no way of being controlled by a computer or any other external device other than what is a part of the cooling system itself. A thermostat can not think on its own. It does what it is told to do....as we all know.

And l am going to write is that I do not believe in a cooling system with no thermostat in it when it is being driven on the street....where I live.

DUB

resdoggie

Lol, yeah, if over explaining dispels the myths surrounding cooling system operation, so be it I guess. But I do get tired of others continually spreading myths. I believe J Hinkley (sp?) stated that a vette never left the factory with a cooling problem. Let's exclude factory race cars available to the public like L-88's. So he's correct if the vehicle is driven within its design parameters of which I have no idea for vettes.

If changing to a lower temp ts to reduce operating temp, as you say, is not gonna solve the problem because the cooling system is obviously not functioning correctly to begin with for whatever reasons to be 30* above the ts rating.

There's at least 4 ways to skin that cat after reading that research paper.

resdoggie

The ts controls itself and modulates between open and shut by the wax pellet melting/solidifying in response to coolant temperature changes. Has its own self contained brain. Its just like any controller, electronic or otherwise, it's driven by feedback. In this case, coolant temperature. For some reason we seem to think of cooling when its warm outside. But there are a few in here who drive year round.....in cold winter weather. Try removing the ts when its -20F and see if the engine finds its own temp of say around 190F. Lol, you'll be using an ice scraper on the INSIDE of your windshield even with the defroster on full tilt! Like you said Dub, no ts is a bad idea.