[Tallguy]

The engine is making a certain amount of heat under whatever conditions are present.

The air flow across the radiator is whatever it is based on the fan type/speed and how fast you are driving.

The amount of air and water flow at any given are really independent of each other. Each changes as engine speed changes and/or fans cycle on or off, etc

Heat exchangers (your radiator) work best at a higher temperature differential (delta T). Faster flow rates will usually yield MORE heat reduction than "holding" water in the radiator longer as the water cools more and the heat transfer becomes less effective. All the while the water in the motor is getting HOTTER. But the motor "wants" a certain temperature hence the thermostat (like a fully mechanical control valve). This also of course helps to get the motor up to that temp more quickly.

It is not an exact science. Obviously there is a large range of flow rates that will work together. Just because you flow water a little slower does not mean you will have a problem as the delta T is still relatively high.

 

[macstang]

I also agree with ditching the flex fan for something that will work better. If you want to stay mechanical get a 6 blade fixed fan and a clutch. A shroud is a necessity with these.


I switched to a BeCool cross flow(tanks on top and bottom so actually it is still a down flow) 3 row radiator and opened up my core support for the 19 inch radiator. I spent quite a bit of time on the core support making it look factory. I just an hour ago got my new 331 running IN the CAR this TIME yehaw, LOL, and it is a bit cool here but my fan now cycles on and off and before with the small 16" fan, even a 3 or 4 row radiator was not enough and once the fan came on it stayed on. I also always had to run an overflow tank because it would puke and it looks like I won't be overflowing this radiator at all.



This is a fundamental. If you make x amount of power you have to run a cooling capacity that fits x and the radiator is a very critical part of that along with the fan's capacity. Doing other things won't ever really fix this problem unless your system has the right capacity but something is not functioning correctly.

 

[zray]

".....My understanding (limited as it is seeing all the comments above) is that the engine heats the coolant up, the radiator cools it down, and once the coolant reaches 190 degrees the thermostat stays open....."

the shop manual is your best friend here. According to Fords engineers who wrote it; the stock 190 F degree thermostat BEGINS to open at 188 F to 195 F. It's not even fully open until the coolant temperature is 210 F to 212 F.**

so its continually opening and closing under "normal" circumstances in order to keep the engine coolant above 190 - 195 and hopefully close to 210 - 212. The safe zone is another 15 degrees hotter, around 225. then it's up to the rest of the cooling system to keep the temp under the danger zone which most agree is not until you get close to 230. running at 210 - 220 doesn't hurt the engine in the slightest.



Briefly, the thermostat will get the engine up to operating temperature as FAST as possible. As GypsyR alluded to, this is to keep the oil happy. No matter which oil one prefers, if you don't get it hot as fast as possible, sooner or later, it will get like the oil GypsyR described. That is why having a thermostat makes sense for all street cars.

Z

** quoted verbatim from the '65/'66 Ford shop manual

 

[1ofAMillion+]

[MENTION=20886]
The ONLY way that "not enough time in the radiator" will cause an engine to over heat is if the radiator is simply not big enough (doesn't have sufficient volume of water capacity).

This perfectly describes the '65/6 radiators:grin2:


PS. Water temps do not dictate engine oil temps.

 

[Brian66]

with all due respect, that strategy does not do anything to keep the engine cooler.

While you are possibly keeping the coolant in the radiator longer, at the same time the engine is not getting replenished with fresh coolant in the same amount that you are "keeping" in the radiator longer. So the engine is heating up more than it would otherwise.

FlowKooler has a write up on their web page somewhere regarding that very theory of yours. And there are numerous articles written by those more highly educated in the physics of fluid dynamics & heat transfer than me, which echo the same argument as FlowKooler.

https://www.flowkoolerwaterpumps.co...m/blogs/cooling-resources/doesnt-coolant-need-more-time-in-the-radiator-to-cool


Z.

I can only relate my experience, and not what I've read in an online article. Prior to the restrictor in the lower radiator hose, without a thermostat, the engine would creep up in temperature to around 215-220 before I shut it down fearing it would overheat. I was talking to a local engine builder who suggested the restrictor. I installed it and the temperature dropped by about 25 degrees.

I should also note that when I had the 4 barrel manifold and 195 thermostat installed, the motor never went above 200. It would hit 200 and then immediately begin to cool down to 195.

However I do love and appreciate a good academic debate....soooo regarding coolant flow rates and their effects on engine temperature in my opinion the article cited is flawed at best. In a conductive cooling system heat energy is transferred by individual molecules bumping into each other (not by the speed of an electron, as the atoms making up water molecules don't lose electrons or pass them along to other molecules), thereby transferring heat from one molecule that is hotter to that which is cooler and so forth until a hot molecule of water brushes up against the molecule of the radiator tube and transfers the heat to the air flowing thru it. His comparison that electrons move faster than the pump and therefore transfer heat at the speed of an electron greater than coolant's velocity created by the pump is simply wrong. Up to a point, the more time the water molecules spend "rubbing" against the aluminum the more heat they can transfer. The more heat those water molecules spend in the outer parts of the column of water inside the radiator shedding heat to the air the more the water molecules in the center of the column can pass the heat to the outer molecules and then out the system to the air. The author also makes several assumptions. He erroneously equates that all aluminum radiators have smaller tubes and therefore they have built in restriction. I was careful to say that my radiator has (2) 1.25" tubes and together have a larger diameter than the lower radiator hose. He also states that RPMs may cause cavitation, which restriction would raise pressure thereby decreasing caviatation but fails to state at which RPM he believes this would occur.

 

[Brian66]

@zray is absolutely correct.
The ONLY way that "not enough time in the radiator" will cause an engine to over heat is if the radiator is simply not big enough (doesn't have sufficient volume of water capacity). That is a capacity problem, NOT a flow rate problem. The whole "not enough time in the radiator" concept and "the thermostat must slow down the flow" argument is simple nonsense.
Sorry if you don't like the language. But this old-wive's-tale must be debunked. I'll put my M.S. Mech. Eng. training, and years of thermodynamic and fluid dynamic study, research and design work, coupled with years of SCCA competition, against whatever background you might have.

I agree that a shortage of capacity can cause overheating but I have also experienced that an unrestricted flow rate can cause similar overheating. Whether the coolant flows too fast thru the engine and doesn't absorb the heat or it flows too fast thru the radiator and doesn't dissipate the heat or unrestricted cavitation occurs or something else may be an academic argument that you should explain to us with your background so we can all understand it better. However, I challenge you to pull the thermostat and run your car in your next SCCA competition.

 

[THE EVIL TW1N]

+1 on getting a different fan.

 

[bmcgc]

All the bits in your engine are designed to work together at temperature.

Ever notice big trucks up north will restrict airflow to the radiator in the winter?

Your best bet is to run the cooling system the way Ford designed it.

 

[Grimbrand]

While the dynamics of engine cooling are pretty deep, let's keep this really simple here:

1) A stock thermostat is very important both in keeping the car cool, and ensuring that coolant temps are where they need to be

2) With too much cooling (which can often be cause by no thermostat, or a low temp one), your oil will also tend to stay cooler, which prevents volatiles from boiling out, and creating sludge.

3) Any car that spends a lot of time stationary or at low speed with the engine running needs a good shroud.

And just one final note: flex blade fans suck, because they don't move as much air, but they rob about as much power as a fixed blade, and they fail frequently, with blades flying off due to fatigue or poor construction. Clutch fans work pretty good, but electric fans cool best and steal the least power. When a car's not moving, but the engine is running, that's when the fan is needed, blowing the most air. Going down the road, air is forced through the radiator without the fan's help. Usually.

 

[zray]

This perfectly describes the '65/6 radiators?.......".

I'd describe them as adequate, as long as everything is up to specs, and no significant hoursepower added. The 65/66's I drove in th 1960's and 1970''s never had cooling issues in town or cross country. Decades later, poor maintenance and the expected internal rust will not be kind to the smallish 65/66 radiators; they begin to show inadequacy when they are filling with sediment, and / or the block does not have good heat transfer due to rust, scale, or other debris.
And also, of course, when another 50-100 HP is making more heat that has to go somewhere.

. "".......PS. Water temps do not dictate engine oil temps.

The descriptive words I would choose to use are "impact" and "influence ". When the coolant temperature is kept too low, or is habitually slow to come up, as in no thermostat, which where this topic began, then the condition of the oil is going to be negatively impacted. As GypsyR pointed out, an engine that runs cold, or is slow to warm up will sooner or later have a poor oil consistency.

Something I'm happy to avoid without feeling the need for experimentation on my dime.

Z

 

[MrFlash]

Cavitation usually occurs when there is a restriction at the water pump inlet.
The pump is pushing water out faster than it can be pulled in through the inlet. This can cause enough of a vacuum behind the impeller blades that the water briefly vaporizes. Water pumps are great at pumping liquids but horrible at pumping gases. Not to mention the rapid erosion caused by the bubbles.
So, if anything, you want the outlet more restrictive than the inlet. Giving the water pump something to push against. And in a way, the thermostat is that restriction at the outlet.
In a perfect world the system would be balanced and inlet volume would always equal outlet volume.

 

[GypsyR]

Designs have changed in the last few years but before that I think we all should have noticed that about everything out there had a lower radiator hose notably larger in diameter than the upper. So there's that.

 

[1ofAMillion+]

Oil doesnt need to get to 212* to dissipate moisture either.

 

[Grimbrand]

Temperatures higher than 212 do a lot better at getting rid of water.

 

[MrFlash]

Oil doesnt need to get to 212* to dissipate moisture either.

Absolutely true.
But it’s even more important for the metal surfaces to be at a warmer temperature so that water vapor, a product of combustion, doesn’t condense into a liquid and fall into the oil.
Which is also a good reason for good crankcase evacuation

 

[PA_cob]

the shop manual is your best friend here. According to Fords engineers who wrote it; the stock 190 F degree thermostat BEGINS to open at 188 F to 195 F. It's not even fully open until the coolant temperature is 210 F to 212 F.**

so its continually opening and closing under "normal" circumstances in order to keep the engine coolant above 190 - 195 and hopefully close to 210 - 212. The safe zone is another 15 degrees hotter, around 225. then it's up to the rest of the cooling system to keep the temp under the danger zone which most agree is not until you get close to 230. running at 210 - 220 doesn't hurt the engine in the slightest.

My question after reading this is what temp should your temp guage read if you are running the 190 thermostat. My engine temp pretty much doesn't cross 195 degrees. Is it running to cool at 195? Makes me question what temp thermostat I am running. I thought it was 190 but now I am thinking it might be a 180.

 

[Grimbrand]

Cob, the factory gauge doesn't read very accurately. If the car doesn't overheat or act weird, then you're probably good. The gauge will mostly just tell you if it's running in its 'normal range'; it doesn't necessarily indicate the actual temperature of your engine. When the needle doesn't point where it usually does, you know there's a problem. If you're not sure about the thermostat, they're really easy to change out, and not expensive either.

 

[zray]

My question after reading this is what temp should your temp guage read if you are running the 190 thermostat. My engine temp pretty much doesn't cross 195 degrees. Is it running to cool at 195? Makes me question what temp thermostat I am running. I thought it was 190 but now I am thinking it might be a 180.

Not too cool.

Sounds like you have an aftermarket gauge. The good ones, like AutoMeter are generally accurate. If your car is a steady 195 F then I think you should consider yourself lucky, and don't worry about changing anything. Be interesting to check the thermostat rating if you have to get in there for some additional reason. But I wouldn't open it up just to see, unless the curiosity is getting the best of you (as it would me )

Z

 

[dobrostang]

Interesting read. Im surprised noone mentioned one of the important functions of a thermostat which is to create a restriction in the system to raise the water pressure which lowers the boiling temp of the colant. If you are determined to remove a thermostat to feed an important superstition in your life, you should replace it with a restrictor plate (speedwar motors etc) or just defeat the thermostat portion of the device and install the restrictor portion to its rightful place.

As for leaving coolant in the radiator longer to cool the cool it more, that’s as controversial as Ginger vs Mary Anne. But putting a restriction in the lower hose will also raise the pressure in the radiator and hoses. Not sure that is advisable in the long run.

My advice is to stop re-engineering a system that has been designed to do the job at hand, and get it to operate as designed correctly. These are well understood systems and this problem has been solved many times. Personally I run a four row copper radiator, Edelbrock water pump and stock thermostat. I can spend an afternoon at Thunderhill at100° All day long then drive home in the same hundred degrees in an hour and a half of bay area stop and go traffic with 400hp.

Get ‘er done...

 

[Redneckgearhead]

Interesting read. Im surprised noone mentioned one of the important functions of a thermostat which is to create a restriction in the system to raise the water pressure which lowers the boiling temp of the colant. If you are determined to remove a thermostat to feed an important superstition in your life, you should replace it with a restrictor plate (speedwar motors etc) or just defeat the thermostat portion of the device and install the restrictor portion to its rightful place.

As for leaving coolant in the radiator longer to cool the cool it more, that’s as controversial as Ginger vs Mary Anne. But putting a restriction in the lower hose will also raise the pressure in the radiator and hoses. Not sure that is advisable in the long run.

My advice is to stop re-engineering a system that has been designed to do the job at hand, and get it to operate as designed correctly. These are well understood systems and this problem has been solved many times. Personally I run a four row copper radiator, Edelbrock water pump and stock thermostat. I can spend an afternoon at Thunderhill at100° All day long then drive home in the same hundred degrees in an hour and a half of bay area stop and go traffic with 400hp.

Get ‘er done...

Isn't that the job of the radiator cap?

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