Shes a runner. I'm curious about running temps of a 403 my gauge in the car is reading just about 205. I still have the 350 thermostat in there. 6 blade mechanical fan. Is 205 okay.

 

What is the thermostat temperature rating? 205 is about right for a 195 thermostat.

 

okay so nothing to worry about cool cool guess I'm used to more modern engines which the gauges show lower

 

Your engine will run just fine at 205 degrees all day long. It would run just fine at 215 degrees. People have this irrational fear of any temperature over 200, which is nonsense. Engines run more efficiently the hotter they are. There is also less chance of incomplete combustion, better boil-off of any condensation in the oil, etc..

The temperature the thermostat opens at is irrelevant. Once it opens, it's done it's job and is out of the picture, and the engine will run at whatever temperature its overall design dictates. The only thing the thermostat does is keep the coolant in the engine, rather than circulating it through the radiator immediately upon start up, so the engine warms up faster. Again, the idea is to get the engine as hot as possible as soon as possible.

 

I don’t know if this is the present operation temp during winter in Wyoming. If it is, the real test comes in 4-6 months. If it remains consistent, there are no worries running around 205*.

​​​​​​….

 

it was almost 60 when we started it up but that is very true as well. Okay just wanted to make sure i don't nuke a brand new engine.

 

Actually many new vehicles run around 215 degrees, it helps emissions. I had all sorts of issues getting my 403 to run cool in my 88 Cutlass. Ended up a GN rad surround finally fixed it. If you have factory overdriven A/C or heavy duty cooling pullies, a 6 or 7 blade fan with a properly functioning clutch and shroud with a factory 4 core or aftermarket big 2 row aluminum radiator, should keep it under 220, closer to 205 to 210 would be more ideal with a 195 factory thermostat. As said, a factory 195 thermostat will run around 205.

 

oh my God

 

Pure water boils at 212 F.
50/50 mix of glycol and water boils at 230 F.
50/50 confined by a 15 PSI pressure cap doesn't boil until 268 F.
I wouldn't worry about anything less than 260 F.

 

That's not particularly helpful. Why don't you just tell him where you think he's wrong?

Maybe we can all learn something.

 

As someone who hit 240 to 260 plus on the gauge, that causes damage to the motor in a very short amount of time. I took out the bearings quickly and actually burnt synthetic blend 5W40 Rotella in my 403. I wouldn't let it get much past 220 for any amount of time.

 

thats funny. it seems learning on here is against the rules.

the latest consensus on here is, the hotter the engine gets, the more efficient it is. the hotter the oil, the less friction there is. blocking the heat crossovers in intake manifolds is a waste of time, and there is no power to be gained

the latest nutty ones…once a thermostat opens, it’s job is done and any temp up to 260 is just fine.

^^^this thermostat^^^ one I’ve shot holes in on here multiple times, yet this bs is still being spread. I’ve explained oil temp and also blocking the heat crossovers….the learning isn’t happening.

 

I have a 78 403 in my 67 Vista Cruiser. Aftermarket aluminum radiator with a 72 shroud,180* thermostat, 7 blade clutch fan with heavy duty clutch. Mine will run 190* almost all the time unless I get in heavy stop and go traffic on a hot day, then it climbs to 215 until I turn on the electric fans in front of the radiator, then it falls back down to 190-200*.

 

There is nothing wrong with 215. You could leave your electric fans off.

I've just returned from a trip where we rented a 2026 Chevy Blazer. It had a temperature gauge, and guess where the gauge parked itself the entire time we drove the car through both city and highway driving. 215 F.

I know it's a different engine and all, but internal combustion is internal combustion. People worry unnecessarily whenever the temperature gets above 199.9, and they shouldn't.

 

oh my God.

 

You're deliberately misstating things. Maybe we should say things to you in words of one syllable or less.

Yes, engine runs better when they're hot, which means fully warmed up, and the quicker they get to that condition the better. That's just a fact of thermodynamics. But it doesn't mean infinitely hot. Engines can also be damaged by running too cool. If not, why don't we strive to run engines at room temperature?

And no one said that an open thermostat will cause the engine to run at 260. The purpose of the thermostat is to allow the engine to warm up as fast as possible. Once the opening temperature is reached, it opens, and the engine is kept at operating temperature by the cooling system.

Simple enough for you?

 

you don’t understand English

an engine does not get hotter quicker with a hotter stat..they get hot at the same rate, the cooler one just opens sooner

a thermostats job is not done once it opens. the stat works just like every other thermostat, like in your trailer. it controls the lower and upper range. it keeps the engine within a specific range.

the wax pellet in the stat expands to force open the stat when the design temp of the stat is reached, as it slowly opens, coolant flows through out the system and is cooled by the rad, this cooler water flows through the engine and stat, cooling the wax pellet, which contracts , this allows the SPRING in the stat to close or restrict water flow ….then the cycle keeps repeating itself to keep the temperature within a RANGE,,usually around 10 above the design temp rating of the stat.

you don’t even understand the basics of a thermostat. you should give up on giving advice if the operation of a thermostat confuses you

 

It does not control the upper operating temp of the engine, only the minimum. The cooling system controls the upper operating temp based on airflow through the radiator. In winter the thermostat can operate as you described, in the southern states with summer temps well into the hundred degree mark the thermostat will stay open and the coolant temp can be higher than 10-15* over the rated temp.

 

oh my God ..again ?

the stat also controls the upper range by regulating the water flow through the engine …at full open, it allows maximum flow to keep the upper range within the maximum over temp ..around 10+ over the max stat rating

why even have a stat temp rating if the temp of its rating and what it does, doesn’t matter?

all engines are designed for the worst case scenario as far as max temp goes. the engineers know the system has to be able to cool the car in the max designed heat it will run in.

changing from a 195 stat to a 160 stat will cause the engine to operate in a cooler range,, like between 160 to 170/175, as opposed to 195 to 205/210

thats called the stat regulating the engine temp according to the range of the thermostat.. it’s constantly opening and closing , partially or fully, depending on the conditions, during running.

 

For what it's worth GM has been running dummy temp gauges for years in cars and light duty trucks. They only have a warm up, running and overheat range. 215 on the gauge represents a huge temp range, like plus or minus 20 degrees.. thats why they stay planted. They started this around 2004. If you had a scan tool and could read actually temp you'd see the gauge is full of $hit. Supposedly folks were constantly bringing there cars back to the dealer and didn't understand that temp fluctuation was normal.

 

The rating on a thermostat is when it starts to open and it may take 10-15* more to fully open. Once it is open, it does not know whether the engine is at the fully open temp or higher. The thermostat is not there to prevent overheating its there to set the minimum engine operating temp and maintain that if it goes lower. Thermostats are mostly effective in winter or cooler days in regulating temp.

 

nope, it’ll stay wide open in that first situation. and, the temp will stay within the operating range, because the whole cooling system is designed to cool beyond any maximum temp it’ll encounter, it’ll stay within its range.

engines are not designed to just run amuck at any temp above the opening point, once the stat opens. there is a RANGE, which is controlled by the thermostat.

look through any thermostat engineering data and you’ll see they are designed to keep an engine within a specific range ..which is designed into the engine and cooling system by the manufacturer.

not just a min and a whatever

 

Here’s a question for the thermostatically challenged on here. If I take out the 195 thermostat in my new 2026 car, and install a 160…. what will happen?

 

Oldcutlass, you pretty much correctly explained it. Don't pay him no mind. He'll keep twisting things til he thinks he won the argument.

 

So what happens if a thermostat fails and sticks fully open?

 

when you can’t refute facts, you quit.

there is no argument…

 

no wonder the most asked question and biggest complaint on this site is..”why does my Olds engine run hot?”

then you see fools tell the guy he needs a hotter thermostat or it’s just fine running waaay over 200deg, like 215+ or more

all my engines run between 160 and 175. because that’s where they make good power and don’t fry the oil.
if you are building something that’s full of emissions and you absolutely need to pass some kind of smog test, put the factory stat in it for the test…then get rid of it

one of the very first mods anyone did back in the 60’s or 70’s to our cars was to put in a low temp stat. Jeez, I wonder why?

 

I want to lower the upper operating temp of my engine temp on my dash gauge from 195 , down to 175, should I take out the 180 stat in it now, and put in a 160 stat?

but I read on the internet the thermostat does not control the upper temp limit,, it only controls the lower temp limit.

I have a new four core rad in it now….maybe I need a five core?
HELP.

 

In Canada a thermostat probably works as you describe as the average temps are much lower than what we see in the southern US. Yes, there are many fools making statements on cooling system suggestions and it's easy to spend other peoples money when it comes to them. When I was kid driving in the mid 70's in New Jersey, a thermostat was not the first thing we changed and nobody I knew swapped in a summer or winter thermostat back and forth. No one ran a 160* in the winter because we liked heat.

 

Its been my experience when checking a thermostat in hot water on a stove with real thermometer, that it begins to open at the rated temp and slowly opens all the way as the temp climbs.. however it stays wide open after that until the water temp drop belows the rated temp, then it closes rather abruptly. It doesn't ease close as the temp lowers.

 

i was waiting for the “I’m in Canada, therefore”

you would be wrong. I’m in southern Ontario where we routinely get well over 90 in the summer. what southern Ontario is also known for is very high humidity because we are sandwiched between the great lakes.

hi humid air is actually harder on a cars cooling system because the air is less dense. in summer we have similar environment to Florida. I’m surround by wine grapes, they harvest into the winter

I was an HVAC tech for 35 years ..I know what I’m talking about when it comes to rads, thermostats and cooling.

a car here in 95 deg temp with humidity in the 80% is harder to cool than a car in 95 Texas dry air.

thermostat; noun. an automatic temperature control device. it means the same in both countries.

 

true. because the spring is forcing it closed. the wax pellets can only expand slow, which is why it opens slower than closing.

 

N Texas is not dry air and cars love 90* temps, try cooling a car when temps are 105+ in the shade. Wall thermostats and engine thermostats are not the same, and heating and cooling a house is not the same as an engine.

 

So what happens if a thermostat fails and sticks fully open?

 

it’ll fail to keep the temperature of the engine within the designed operating range.

 

wall thermostats are automatic temp control devices..exactly the same as an automobile stat.

they are designed to keep something within a specific temp range.

in a car, they regulate the water flow throughout the cooling system to keep the engine within a specific temp range.

 

You’re contradicting what you posted earlier.

 

Wall thermostats do not keep temps within a range, they are set to the minimum temperature that you want your space to be. Depending on what it is set to, for heat it turns the heater on if the temp drops below the set temp, and for cooling it turns the a/c on if the temp is above the set temp. It does not do both at the same time.

How does the thermostat in a car control the temperature if it slowly keeps creeping up once it's fully opened? How does your home thermostat cool the house back down when set to heat if the temperature keeps rising past it's set temp or when set to cool keeps dropping way below the set temp?

 

This is what I don't understand ... other than opening fully, what control can an automotive thermostat exert over upper temp registers?

 

Directly from a thermostat manufacturer. it keeps the engine within a specific temp range .
it prevents overheating, that’s what’s called the upper range.