[Schurkey]

If a lower-temp thermostat doesn't lower engine temp at idle or cruise, you have a cooling system problem. (Or an electric fan system)

[STEELCITYFIREBIRD]

Your cooling system has to have enough head room to run a constant temp under the most demanding conditions.


Belt slipping at higher RPM with aggressive pitch fans is very often an unseen problem.
Air in your cooling system is another common unseen problem.

[Firebob]

I normally run a 160 Thermo and temps are in the low 200 range. I may swap it out for a 190 this weekend and see if it makes any kind of difference in running temp without touching anything else. Easy experiment and won't cost anything but a bit of time.

[RocktimusPryme]

Originally Posted by Firebob

I normally run a 160 Thermo and temps are in the low 200 range. I may swap it out for a 190 this weekend and see if it makes any kind of difference in running temp without touching anything else. Easy experiment and won't cost anything but a bit of time.

I would be curious of those results for sure.

[AG]

My '72 LeMans has a 9.0:1 CR 455 with a RAIV cam and iron heads and has the stock 350 2 bbl radiator. I run a 160 F T-stat and a 7 blade flex fan and the car will only get to 170-175 F on a 90 F day. I have to change the T-stat to a 180 F one to raise the temps because it runs too cool on days below 80 F.

[Carmine]

Originally Posted by Firebob

I normally run a 160 Thermo and temps are in the low 200 range. I may swap it out for a 190 this weekend and see if it makes any kind of difference in running temp without touching anything else. Easy experiment and won't cost anything but a bit of time.

Looking forward to seeing those results myself.

My pretty much stock '71 GTO, has a 180 thermostat. From a cold engine, it takes several miles before the temp. reaches 180. Seems like a very slow process. It will stay at 180 for a while and with the same driving, will reach 195. It seems to like that temp. best and will stay there almost indefinitely; again depends on my driving. I'm have 3.55 gears, TH400 trans., about 45-50 mph. Probably taching around 23-2500 rpm's. Just this past Sunday, went to a car show with it. Went the back way to avoid the interstate where you have to go 60-65 mph or get run over. No problem going over. It was a long day and I decided the shortest, quickest way home was the interstate. It was about 85 degrees out with no humidity. Jumped on the interstate and got up to speed. Mostly 65 mph. Could hear the motor working at about 3000 rpm's. Temp. creeped up to about 210. Came to a very steep, long grade and kept up my speed. Temp. then went to 230 and made me nervous. It seemed to stabilize at that temp. and thankfully I was done with the grade. Going down hill, the temp. reduced itself to about 210. Got off on a primary road and lowered my speed. Temp. went down to about 200-205 but never did reach the 195 mark again. Seems it had a hard time getting rid of the heat once it was there. I've owned 5 GTO's and they have all run warm. Never overheating, just hotter then I would like. I know many members here have great success with their engine temps., and I'm happy for them, but I'm not one of them. I really believe they are prone to running hot, Carmine.

[Carmine]

Originally Posted by Schurkey

If a lower-temp thermostat doesn't lower engine temp at idle or cruise, you have a cooling system problem. (Or an electric fan system)

Just trying to understand this, but are you saying that a lower temp. thermostat such as a 160, will keep your engine running cooler then lets say a 180 or 195?? Thanks.

[steve25]

Let me use a example of my buddy's car to make a point here if you will allow?

Something's to note when you look at this picture.

On these 68 ( A, B and F body's ) and up cars the fan shroud is much deeper then the previous years.

The stock fan resides as it should half in and half out of the shroud.

The air block on top of the rad support to the nose support is in place.

The car makes use of a 4 row Harrison rad.
The T stat is a 190.

What you can't see is that the water pump to impeller clearance was reset to what it needs to be, as this is a major factor in cooling the motor.

This motor now has 200 miles on it and the paint on the Exh ports has yet to turn color, yet start to burn off, granted the heads are Aluminum, but still it a point to note!

This the same radiator used in the 1970 Chevy 450 hp BB set up and they could run all day flat out and not have a cooling issue if they where rolling along at more then 50 mph.

My buddy's car here is a 511 cid, so it's a good percent larger then a 455 and at 700 hp its making some 46% more hp then the 450 hp BBC motor that could have come in this A body model.

During our drive to a cruse nite this week I watched his temp gauge Constantly and even when he blasted full throttle thru the gears the temp never topped 205 and then once out of the throttle was back down to 195 in 2 minutes of driving and the air temp was 87 on that day.

In short proper jetting , timing and a good cooling system that gets the needed amount of air through it is key to a keeping a motor out of danger, not a 160 rated T stat!

[Firebob]

Well this is kind of the thing that I was getting at with the effects of underhood heat. I know that the Doug's introduce ALOT of heat to the engine compartment and early Fbodys are notorious for not evacuating the heat with any kind of efficiency even in stock form. Add 10.7 CR, 500hp and headers that probably would glow in the dark under normally running temp and its definitely a puzzle to be worked out. So far it doesn't seem like the Taurus fan is the magic bullet that some tout it to be, for my car anyway.

I can't really see how changing from a 160 Thermo to a 190 will make any difference because they will both be fully open at the point where the heat begins to be an issue. Seems like it would only limit open flow for a bit longer for faster warm up time. But it won't cost anything and it takes one for thing out of the equation.

[Sirrotica]

More airflow, and a waterpump that is matched to the system is where you begin to efficiently cool a Pontiac. Adding capacity to the system can help, but it would be tough in a street car.

A waterpump that is trying to pump too much through a restricted system will actually build more heat due to the friction of the water. Aeration/cavitation of the water also reduces it's heat transfer capabilities.

Sometimes the touted restricting the waterflow doesn't solve the problem that some think water moving too fast through a system to reject heat, what happens is the pressure in the block is raised making the coolant boiling point higher, and not turning to steam internally. It's a balancing act that has no tried and true formula, because almost every one of our cars has some differences.

The clearance of the plates is important to stop cavitation inside of the system and many times is a magic bullet by itself, but sometimes it only minimally improves the problem. Usually there is not only one factor contributing to heating problems, maximizing all the variables is what solves the problem many times.

Sucking a radiator hose closed at higher RPM is a tough problem to find, just make sure the lower hose has a spring inside of it on every car.

[Formulas]

Some of us like to drill holes in the outer flange of the thermostat what I have found is my engine stays closer to the thermostat rating and if it does get warmer with spirited driving it dives back down quicker.

But it drives some people on this site crazy just to mention it

It is more flow and NOT a vast departure from OE.
.

[Scott65]

Originally Posted by Firebob

I normally run a 160 Thermo and temps are in the low 200 range. I may swap it out for a 190 this weekend and see if it makes any kind of difference in running temp without touching anything else. Easy experiment and won't cost anything but a bit of time.

Don't expect a change unless your current thermostat isn't working correctly. Been there done that. But it will allow you to verify condition of current one.

[Carmine]

Originally Posted by Sirrotica

More airflow, and a waterpump that is matched to the system is where you begin to efficiently cool a Pontiac. Adding capacity to the system can help, but it would be tough in a street car.

A waterpump that is trying to pump too much through a restricted system will actually build more heat due to the friction of the water. Aeration/cavitation of the water also reduces it's heat transfer capabilities.

Sometimes the touted restricting the waterflow doesn't solve the problem that some think water moving too fast through a system to reject heat, what happens is the pressure in the block is raised making the coolant boiling point higher, and not turning to steam internally. It's a balancing act that has no tried and true formula, because almost every one of our cars has some differences.

The clearance of the plates is important to stop cavitation inside of the system and many times is a magic bullet by itself, but sometimes it only minimally improves the problem. Usually there is not only one factor contributing to heating problems, maximizing all the variables is what solves the problem many times.

Sucking a radiator hose closed at higher RPM is a tough problem to find, just make sure the lower hose has a spring inside of it on every car.

A water pump was mentioned a few times in this thread. Do you have a preference as to the best water pump to use?? Thanks.

[Sirrotica]

GMB is an aluminum casting with a cast iron impeller, new at Summit $48.68.

https://www.summitracing.com/parts/g...w/make/pontiac

I've had good luck with GMB pumps previously. I used Gates also, but I couldn't find any. They might not be manufacturing them any longer.

[Formulajones]

Originally Posted by steve25

Let me use a example of my buddy's car to make a point here if you will allow?

Something's to note when you look at this picture.

On these 68 ( A, B and F body's ) and up cars the fan shroud is much deeper then the previous years.

The stock fan resides as it should half in and half out of the shroud.

The air block on top of the rad support to the nose support is in place.

The car makes use of a 4 row Harrison rad.
The T stat is a 190.

What you can't see is that the water pump to impeller clearance was reset to what it needs to be, as this is a major factor in cooling the motor.

This motor now has 200 miles on it and the paint on the Exh ports has yet to turn color, yet start to burn off, granted the heads are Aluminum, but still it a point to note!

This the same radiator used in the 1970 Chevy 450 hp BB set up and they could run all day flat out and not have a cooling issue if they where rolling along at more then 50 mph.

My buddy's car here is a 511 cid, so it's a good percent larger then a 455 and at 700 hp its making some 46% more hp then the 450 hp BBC motor that could have come in this A body model.

During our drive to a cruse nite this week I watched his temp gauge Constantly and even when he blasted full throttle thru the gears the temp never topped 205 and then once out of the throttle was back down to 195 in 2 minutes of driving and the air temp was 87 on that day.

In short proper jetting , timing and a good cooling system that gets the needed amount of air through it is key to a keeping a motor out of danger, not a 160 rated T stat!

That's running hotter than my fathers 571 ci, lol. After the changes I made last weekend we couldn't get his engine over 165 degrees pushing 3,000 rpm for miles on an 85 degree day here.
Yes, I would say proper jetting and timing events are a big player here, can't stress that enough, and the fact that his tune is spot on is probably what kept the car from overheating in the first place when he had a poorly designed shroud and electric fan setup on it, because the addition of a the original shroud and clutch fan dropped his cooling temps more than 30 degrees with no other changes.

[Formulajones]

Originally Posted by Firebob

Well this is kind of the thing that I was getting at with the effects of underhood heat. I know that the Doug's introduce ALOT of heat to the engine compartment and early Fbodys are notorious for not evacuating the heat with any kind of efficiency even in stock form. Add 10.7 CR, 500hp and headers that probably would glow in the dark under normally running temp and its definitely a puzzle to be worked out. So far it doesn't seem like the Taurus fan is the magic bullet that some tout it to be, for my car anyway.

I can't really see how changing from a 160 Thermo to a 190 will make any difference because they will both be fully open at the point where the heat begins to be an issue. Seems like it would only limit open flow for a bit longer for faster warm up time. But it won't cost anything and it takes one for thing out of the equation.

It won't Bob, least not from my experience. There is that whole heat transfer formula theory that guys mentioned on the thread I started about finding the cooling issues on my fathers car, but I've moved thermostats around and the only thing I found is that the hotter thermostat will force the engine to run that temp, but the colder one will only run colder if the rest of the cooling system is capable of pulling it down that far. If it's not, then the temp will run where it will run. That's pretty much the gist of it. If you run a 160 and your temps are always 200+ then you clearly have something in the cooling system holding you back.

I don't think a single Taurus fan would cut it for you Bob considering where you live and what you're doing. The first gens don't have as much radiator in them either. Hard to beat a stock shroud and a good 7 blade clutch fan.

[dataway]

Yep ... if an engine is overheating with a 180 in it .... a 160 will not help a bit, not even a little.

A thermostat regulates the temperature of an engine with a properly configured cooling system .. it does absolutely nothing to assist in the cooling process.

If the system can't maintain the temperature rating of the thermostat the problem is elsewhere. It is no different than the thermostat on the wall in your house ... if the house doesn't get cool enough ... it's not thermostats problem (assuming it's not broken), it's that the system does not have the ability to remove enough heat.

Lot of threads on this subject, and a very interesting subject. Probably the most commonly misdiagnosed issue that people encounter with there vintage or hot rod cars.

Personally my advice would always be to go back to an OEM system with KNOWN good components and then progress to other more radical solutions if that doesn't work. And "known good components" does not mean a 40 year old radiator that you look into the hole and say ... "yeah that looks pretty clean"

[Carmine]

Originally Posted by Sirrotica

GMB is an aluminum casting with a cast iron impeller, new at Summit $48.68.

https://www.summitracing.com/parts/g...w/make/pontiac

I've had good luck with GMB pumps previously. I used Gates also, but I couldn't find any. They might not be manufacturing them any longer.

I just took a look at that water pump. It got very good reviews. Question. It was mentioned that on some engines, the hub height can be different. It's 4" vs. 4.5".
Not sure I understand this completely. Does this mean that the fans depth into the shroud could change?? If so, how important is that?? Thank you, Carmine.

[Steve C.]

One source of many out there.....

"If you’re running a belt-driven fan, there are a few things you need to do in order to maximize the engine cooling that the fan can provide. It’s critical that the fan be positioned properly within the fan shroud and that there is just enough clearance around the fan blades."

https://www.flex-a-lite.com/blog/the...roud-position/


( Information provided in this post does not represent a product endorsement. And unless specified it is not based on personal experience and is offered for general interest only )



.

[grivera]

Originally Posted by dataway

Yep ... if an engine is overheating with a 180 in it .... a 160 will not help a bit, not even a little.

A thermostat regulates the temperature of an engine with a properly configured cooling system .. it does absolutely nothing to assist in the cooling process.

This - a thermostat is designed to regulate minimum temperature only