I put a 160 t-stat in my BBC during the summer because in summer time, it runs hotter than I want it to. Despite the 160, in the summer, it stays around 185 unless I'm at a light too long.

But in the days that I get to occasionally drive it in Winter, it stays pegged on 160. I think that is too cool. Am I wrong?

I also want to boil out any condensation in the engine that may be in there.

Should I put a 180 in for Winter?

I would use a 180 degree HIGH FLOW thermostat all year.

Haha I'm having an opposite issue on my 327 in my Nova, I have a large 4 core brass radiator I just had rodded out, and I put a Mr Gasket HIGH FLOW 180 thermostat. I can't get it to go over 170!! Literally idling in my driveway its 170 and won't go any higher no matter what. I know the mechanical autometer gauge works because before it would do 180-185. But with my new shroud (had no shroud before) and the 17" Flexalite fan + Flexalite Thermal Clutch I can't get it to budge 170. Now get this, if I drive the car, it won't budge 160 !!! Literally the thing stays at 160 while driving. Sounds like the new high flow thermostat is stuck open but its not, I checked!
I might have to go to a regular flow 180 to cause it to flow less. I also did a few other changes when I rebuilt the top end including a new Proform high flow alum water pump, 180 high flow thermostat, new hoses, rodded out the 4 core, small block shroud to protect my fingers. I'm already running a smaller diameter March Performance water pump pulley, might have to go a little smaller if the regular flow thermostat doesn't fix the issue.

i've never seen an engine that a good stock water pump with a good stock thermostat can't cool. if the pump and stat are working properly, it shouldn't matter how big you go with the radiator. it will always maintain the temp of the stat.

Yea I'm going to hook up another temperature gauge I have that I use to use in my Camaro, something is not right with my stat, I just tooled around at 155-160 degrees, so either that stat is opening way too soon or the gauge is off by 20-25 degrees.

Haha I'm having an opposite issue on my 327 in my Nova, I have a large 4 core brass radiator I just had rodded out, and I put a Mr Gasket HIGH FLOW 180 thermostat. I can't get it to go over 170!! Literally idling in my driveway its 170 and won't go any higher no matter what. I know the mechanical autometer gauge works because before it would do 180-185. But with my new shroud (had no shroud before) and the 17" Flexalite fan + Flexalite Thermal Clutch I can't get it to budge 170. Now get this, if I drive the car, it won't budge 160 !!! Literally the thing stays at 160 while driving. Sounds like the new high flow thermostat is stuck open but its not, I checked!
I might have to go to a regular flow 180 to cause it to flow less. I also did a few other changes when I rebuilt the top end including a new Proform high flow alum water pump, 180 high flow thermostat, new hoses, rodded out the 4 core, small block shroud to protect my fingers. I'm already running a smaller diameter March Performance water pump pulley, might have to go a little smaller if the regular flow thermostat doesn't fix the issue.


With my new water pump pulley, it is underdriving the waterpump so its cooling a little better.

Where do I find a high flow t-stat? Are they normally at autoparts stores?

www.jegs.com
www.summitracing.com
your local performance shop

Part number MRG-4364, made by Robertshaw. In fact, all are made by Robertshaw.

Brian, thermostats are not exact, expect a +/-10* error. Your temps are fine for the thermostat chosen, IMO.

Note that it is the cooling capacity of the system that determines the maximum operating temp. The thermostat only determines the minimum.

Mike, your system is operating normally, but your cooling system is marginal. It can't throw off all the heat in warmer weather.

With my new water pump pulley, it is underdriving the waterpump so its cooling a little better.

Where do I find a high flow t-stat? Are they normally at autoparts stores?

How does underdriving the pump make it cool better?

How does underdriving the pump make it cool better?

The coolant travels through the engine slower and thus picks up more heat. The coolant will come back to the radiator with closer to the maximum amount of heat that it can handle.

I've also heard that over driving the water pump can cause cavitation and the system is then even less efficient.

Now that I have this new belt dirve system that under drives my pump, I'll bet my cooling will be better in the summer months.

I've already noticed a change.
Consult with Dawg69 about it, he turned me onto this system and its more than about just looks. It guarantees I'll never throw an alternator belt and I think the car cools more efficiently. Plus, its convenient, I can take off the v-belt to the power steering pump and be ready to race without worrying about P/S robbing some power from the engine....

The coolant travels through the engine slower and thus picks up more heat. The coolant will come back to the radiator with closer to the maximum amount of heat that it can handle.

I've also heard that over driving the water pump can cause cavitation and the system is then even less efficient.


Higher coolant flow will ALWAYS result in higher heat transfer. Coolant cannot absorb heat after it reaches it's pressure corrected vapor point. Furthermore, coolant absorbs heat at a progressively slower rate as it approaches this point.

http://www.stewartcomponents.com/tech_tips/Tech_Tips_6.htm
http://www.stewartcomponents.com/Tech_Tips.htm

Higher coolant flow will not ALWAYS result in higher heat transfer. I'm not saying the slower the better but definitely the faster the better doesn't ring true either. I'm saying that I am running the pump slower and it is definitely cooling better.

Now that I have under driven the water pump, it is cooling so well that its too cool and I have to move the t-stat up to a 180.

Higher coolant flow will ALWAYS result in higher heat transfer. Coolant cannot absorb heat after it reaches it's pressure corrected vapor point. Furthermore, coolant absorbs heat at a progressively slower rate as it approaches this point.]
so, how come i've seen cars that overheat when you take the thermostat out and allow the water to flow without any sort of restriction? in fact, most cars will eventually overheat if yo take the t-stat out.
and how come the NASCAR guys run different restrictors in their cooling system instead of letting the water run without any restriction? they control the engine temps by changing how much air they let thru the radiator, not with a t-stat.

so, how come i've seen cars that overheat when you take the thermostat out and allow the water to flow without any sort of restriction? in fact, most cars will eventually overheat if yo take the t-stat out.
and how come the NASCAR guys run different restrictors in their cooling system instead of letting the water run without any restriction? they control the engine temps by changing how much air they let thru the radiator, not with a t-stat.

What's revolutionary about controlling temperature by controlling the air through the radiator? Isn't that what a clutch fan does? A temperature controlled electric fan? Not a new concept at all.

What are you assuming here? Does the removal of the thermostat affect only the flow? Does it affect any other parameters of the system?
Are you assuming that the actual mass flow is greater with the thermostat removed? If you aren't assuming it how did you measure it?
Are you also assuming that the reduction in head pressure on the pump allowed for a decrease in the PCBP of the coolant? You must remember that as the PCBP is decreased, the ability of the coolant to absorb heat is also decreased. Once you have a departure from nucleate boiling your cooling efficiency is significantly reduced as you end up with an insulating layer of steam between the coolant and the metal.
When you removed the thermostat did you also plug the bypass? According to Evans this will cause the pump to scavenge through the bypass port and reduce the cooling effectiveness.

Count the black dots in the center of the wheels.

http://www.uniklinik-freiburg.de/augenklinik/live/homede/mit/bach/ops/mdia/rotsnake2.gif

Would you assume that the wheels are rotating?

i just assume that pretty much every car i've ever seen with no thermostat has overheated, and by simply putting in a thermostat it has stopped overheating... and if the more volume you ran thru the engine, the better it cooled, then why do the racecar guys run restrictors in the upper radiator hose to prevent the car from running too hot, if not to slow the water down to allow it to collect more heat energy while in the block and allow it more time to shed the heat while in the radiator?
i don't claim to know the answers -THAT'S WHY I ASKED..
and what does the way the mind processes a visual thing like you posted have to do with cooling systems?

Yea I'm going to hook up another temperature gauge I have that I use to use in my Camaro, something is not right with my stat, I just tooled around at 155-160 degrees, so either that stat is opening way too soon or the gauge is off by 20-25 degrees.
I like to test stats before installation.I fill a steel can with water and heat it on the stove.You can watch the stat open while monitoring the temp with a meat thermometer.:thumbsup:

i just assume that pretty much every car i've ever seen with no thermostat has overheated, and by simply putting in a thermostat it has stopped overheating... and if the more volume you ran thru the engine, the better it cooled, then why do the racecar guys run restrictors in the upper radiator hose to prevent the car from running too hot, if not to slow the water down to allow it to collect more heat energy while in the block and allow it more time to shed the heat while in the radiator?
i don't claim to know the answers -THAT'S WHY I ASKED..
and what does the way the mind processes a visual thing like you posted have to do with cooling systems?

I was gonna say, the pretty designs have nothing to do with this conversation at all.
I have underdriven my pump and now the cooling is too good. Now I NEED a higher t-stat when before I needed a lower one because the smaller pulley was moving coolant faster. It wasn't cooling good enough.
Now it is with the bigger pulley.

I'm certain that if I went too big, the cooling would get worse.

i just assume that pretty much every car i've ever seen with no thermostat has overheated, and by simply putting in a thermostat it has stopped overheating... and if the more volume you ran thru the engine, the better it cooled, then why do the racecar guys run restrictors in the upper radiator hose to prevent the car from running too hot, if not to slow the water down to allow it to collect more heat energy while in the block and allow it more time to shed the heat while in the radiator?
i don't claim to know the answers -THAT'S WHY I ASKED..
and what does the way the mind processes a visual thing like you posted have to do with cooling systems?

http://scienceworld.wolfram.com/physics/nimg45.gif

Newtons law of cooling states that the greater the difference in temperature between the cooling medium and the cooled medium the greater the rate of heat transfer.
If I was to tell you that my car runs hotter in the summer time than the winter time, you would probably conclude that it's because the air is colder in the winter and cools the engine better. It's just a demonstration of Newton's law of cooling, the difference between the mediums is higher in the winter and more heat is removed.
Another way to increase the rate of heat transfer is to pump as much hot water as possible through the radiator, keeping the average temperature of the radiator as high as you can. A hot radiator is more efficient than a cool radiator, it will remove more heat from the engine.
There is no 'time' as such when it comes to water being in the radiator. The time you are concerned with is the time it takes to remove the excess heat you are generating, i.e. the rate of heat transfer. If my radiator is very hot and removes heat at twice the rate as your cooler radiator, I can make much more horsepower before the outlet temperature of the engine goes too high. One constant of cooling systems is the average temperature of the radiator for a given load. If I slow the flow of water to allow the outlet of the radiator to cool, the inlet of the radiator will have to be warmer to compensate.
Racecar guys run restrictors to keep the water pump from cavitating. It also raises the pressure in the block and raises the boiling point. If the pressure goes down you may enter the area of the curve known as departure from nucleate boiling ( or film boiling ), and the heat transfer will be reduced. If you can't transfer heat to the coolant your engine will get real hot real quick. Racecar guys also run their engines at 7000+ rpm for extended periods of time, a feat most street car guys won't attempt.

http://www.rotaryeng.net/Heisler-nuc-boiling.jpg


Here is some good reading on the physics of cooling and some reading on automotive cooling systems. There will be a test on this.

http://www.wlv.com/products/databook/ch5_1.pdf
http://www.arrowheadradiator.com/14_rules_for_improving_engine_cooling_system_capab ility_in_high-performance_automobiles.htm
http://www.delphi.com/pdf/techpapers/2000-01-0939.pdf
http://www.stewartcomponents.com/Tech_Tips.htm

ok.. but what was with the pinwheel thingamajig?

at least we agree that a restriction is necessary for good cooling most of the time. that's all i was trying to say. the sad thing is that we actually almost totally agree, but i don't have all that fancy book learnin' to fall back on. i just know what i've seen.
in a nutshell- on a street car, you need a t-stat that cuts off water flow thru the radiator until the engine reaches a certain temp- where it opens up and allows flow, but is still somewhat of a restriction to "slow down" the water thru the system and prevent cavitation of the coolant. then, you can either use radiator sizing, airflow thru the radiator, the t-stat, or some combination of those elements to maintain a steady operating temperature.

are we on the same page here, or do i need to look at more pinwheels? :)

but what was with the pinwheel thingamajig?

It's an illusion, it appears that the wheels are rotating but the really aren't. Or are they? It means that something appears to be happening that really isn't. The same thing occurs when a restrictor is used in a sprint car cooling system. Some would assume that this reduces the flow of coolant and is the reason for the improved operation of the cooling system, when the laws of physics would contradict this observation. How many guys do you know that have actually measured the flow in their cooling systems? Have they tested for cavitation, turbulence, mass flow, etc?
Why does a thermostat open when the engine gets hot? Is it to restrict the flow of coolant or to allow more coolant to flow? If my thermostat sticks closed, does the engine stay cool or will it heat up?
There is no 'knee' in the flow curve, the more mass I can flow through the radiator, the better it works.
You don't need 'fancy book learning', you can read about most anything you want on the internet. Did you read about cooling?

when did i say that a car won't overheat if the t-stat stays closed?
now i think you are just looking for an argument..
and, yes, the more heat you get to the radiator, the more it can release into the airsteam.
but an efficient radiator is but one part of a cooling system.
if you ram the cold water thru the hot engine at breakneck speeds, it will not pick up any heat to take to the radiator..and then things get hot.
hence those things that every speed catalog calls "restrictors"- and that's what they do, they "restrict" the flow of coolant which leads to slightly higher pressure in the block and more heat hadling capacity in the coolant- or a thermostat that still restricts even when all the way open.
we are saying the same thing here, just with different words..

Thanks, nova for the links. Test will be multiple choice or True/False?

Again, the battle between alum rads & copper/brass rads on the best heat dissipator.
Arrowhead states copper/brass.
Stewart states alum.

So a hotter radiator is better?
Only 10*F difference by design between inlet & outlet?
Smaller radiator may be better, all else being equal?

Kind of hard to move/relocate a rad size condensor to have decreased ambient air across rad.

when did i say that a car won't overheat if the t-stat stays closed?
now i think you are just looking for an argument..
and, yes, the more heat you get to the radiator, the more it can release into the airsteam.
but an efficient radiator is but one part of a cooling system.
if you ram the cold water thru the hot engine at breakneck speeds, it will not pick up any heat to take to the radiator..and then things get hot.
hence those things that every speed catalog calls "restrictors"- and that's what they do, they "restrict" the flow of coolant which leads to slightly higher pressure in the block and more heat hadling capacity in the coolant- or a thermostat that still restricts even when all the way open.
we are saying the same thing here, just with different words..

We're not saying the same thing. Why would you believe that the water would transfer less heat if it goes through the engine rapidly? It makes no difference which particular unit of water happens to be in the engine at any particular point, it just goes round and round through the cooling system. If you happened try reading some of the reading materials I referenced, you would come across a recurring theme, which is:

- IMPROVEMENT RULE # 1 -
Anything you can do to increase the coolant flow rate, within limits described, will improve heat transfer and cooling performance. Anything you do to restrict or reduce the coolant flow rate will hurt cooling performance

http://www.arrowheadradiator.com/14_rules_for_improving_engine_cooling_system_capab ility_in_high-performance_automobiles.htm

Higher coolant flow will ALWAYS result in higher heat transfer. Coolant cannot absorb heat after it reaches it's pressure corrected vapor point. Furthermore, coolant absorbs heat at a progressively slower rate as it approaches this point.
http://www.stewartcomponents.com/tech_tips/Tech_Tips_6.htm

The Evans pumps, radiators, and other components improve cooling by increasing the coolant flow velocity through the engine and radiator.
http://www.evanscooling.com/main20.htm

The faster it flows, the more turbulence is created and the more heat is exchanged. Turbulence has been shown to increase the heat flow by 150-500%. There's a lot of info available from overclockers about the effects of cooling cpu's with water. Here's some interesting articles on water cooling physics:
http://www.overclockers.com/articles511/index02.asp
http://www.overclockers.com/articles481/index06.asp

You reference the heat handling capacity of the water, which is the highest it will be at low temperatures. As the water gets hotter, it can absorb less heat.

Given your views on flow, can the air go through the radiator so fast it won't pick up any heat? Would a smaller fan cool better?

Another interesting exercise is to calculate the average amount of time that the water spends in the radiator for any given flow rate.
If I have a 20 quart system with 15 quarts in the engine and 5 in the radiator and hoses, how many seconds of each minute does the water spend in the engine at 25 gpm pumping rate? 50 gpm?

If the optimum velocity of coolant flow through the radiator is 6-8 feet/sec ( per Arrowhead ), how many gpm would be optimum for a crossflow radiator with 24" long tubes that holds 1 gallon in the tubes?

25 GPM = 12 seconds
50 GPM = 3.3 seconds

Optimium GPM w/b 42 GPM

I hate fill-in the blank.

Extra credit?

Whew!!!!
The way I tell if my stuff is working well is to feel all the heat being thrown off the car when standing next to it while it idles. No/less heat = a too hot engine. And that heat I feel is a function of the radiator,,,,right? And I like multiple choice.

25 GPM = 12 seconds
50 GPM = 3.3 seconds

Optimium GPM w/b 42 GPM

I hate fill-in the blank.

Extra credit?

If I have 3/4 of my water in the engine and 1/4 of it in the radiator, the water will spend 45 seconds of each minute in the block no matter how fast you pump it. If I have a 5 gallon system and my pump is rated at 25 gpm, the water will be completely cycled through the engine every 12 seconds. A particular molecule would spend 9 seconds in the block and 3 seconds in the radiator each cycle. If I double the flow rate, the cycle time is cut in half, to 6 seconds total, but the water still spends 3 times as much time in the block as in the radiator, 4.5 seconds in the block, 1.5 seconds in the radiator.

If your radiator is 24" long and has a gallon of fluid in the tubes, you would have 2 ft/sec velocity if you pumped 1 gallon/sec. In order to get 6 ft/sec velocity you would have to pump 3 gallon/sec thru the radiator, or 180 gpm. At this rate in our example 5 gallon system, we would cycle the water completely every 1.67 seconds.

yes, a smaller fan with a closed stat is the way to go.
that's exactly what i said. you win. you smart. me dumb..

When someone argues with him, he has to try and talk over our heads. Its a defensive measure. He went to college therefore, he HAS to be smarter than us.

Didn't Wile E. Coyote feel he was smart too?

When someone argues with him, he has to try and talk over our heads. Its a defensive measure. He went to college therefore, he HAS to be smarter than us.

Didn't Wile E. Coyote feel he was smart too?

This is a discussion of basic stuff covered in high school physics classes. At least it was studied when I went to high school. This isn't brand new stuff that suddenly appeared on the internet, discovered last week. Most of the laws of physics covering thermal effects have been known since the 1700's.

I sure did go to college, four years in the Marines got the GI bill to pay the cost. No way I was going to waste a chance at a mostly free college education. College doesn't make you smart, just educated. Plus it will avail you an average of $600,000 more salary during your working lifetime compared to a HS degree. You're never too old to get an education.
Some info on the value of education:
http://www.tracer2.com/admin/uploadedpublications/1042_tlmr0312art.pdf

Here's some more education on cooling systems from Evans. Interesting take on what temperature to run the motor:

http://www.evanscooling.com/articles/aug97ct.htm

This is a discussion of basic stuff covered in high school physics classes. At least it was studied when I went to high school. This isn't brand new stuff that suddenly appeared on the internet, discovered last week. Most of the laws of physics covering thermal effects have been known since the 1700's.

I sure did go to college, four years in the Marines got the GI bill to pay the cost. No way I was going to waste a chance at a mostly free college education. College doesn't make you smart, just educated. Plus it will avail you an average of $600,000 more salary during your working lifetime compared to a HS degree. You're never too old to get an education.
Some info on the value of education:
http://www.tracer2.com/admin/uploadedpublications/1042_tlmr0312art.pdf

Here's some more education on cooling systems from Evans. Interesting take on what temperature to run the motor:

http://www.evanscooling.com/articles/aug97ct.htm


I would be panicking if my engine was running at 260. I would be pretty nervous even at 230 as they describe.

My engine runs cooler now that I've underdriven my pump. Too cool in fact so I must move up to a higher t-stat. 230 is too hot for my tastes, I'll stick with 180.
High flow was it?

most new cars are designed to run at 230 and even 240 degrees. seems nuts, but with a pressurized system, very doable. hell, i've heard of NASCAR guys on tv running at 260 and not worrying about it.
i've got my Monte running in the 200 range when on the open road, but that gets kicked down to 190 in town because of the fan temp switch i got at NAPA. it comes on at 210 and kicks off at 190. but thru the use of aluminum sheets blocking off about 3/4 of the airflow thru the grille, i got the temp range to stabilize at 200 on the interstate without the fans ever kicking on and drawing power from the alternator. it also helped with the mpg. i gained more from blocking off the grill than i did by going to an overdrive tranny. and it feels more stable, too.



and i still say we (onovakind and myself) were saying the same things- just using a different vocabulary.

u 2 sound like an old married couple...lol...i also feel that 230-260 is too high, especially with aluminum heads with totally different expansion rates than cast iron...maybe it just seems bad, but is really good...or maybe i`m just spinning my wheel thingamajiggies...lol...