Technical New AC…and now SBC runs 30 degrees hotter

Heat Transfer is DIRECTLY and or Cooling is Directly Related to Time and Flow plus Surface Area. A thermostat is Dual purpose you are half right, Old Quick 8 Door Slammer series in the South years ago ran Washers in place of Stat. If engine is @ 183 degree's it will Expand Stat Spring on a 180 Setpoint, Water pump will push in or Pull 160 degree water, water will close Stat @ 163, engine will Heat water back to 183, Rad will cool water back to 163. If you don't understand this Elementary Fact, you are no Mechanic Period.

 

Depends on the ambient if it will cycle like that, most engines , once heated , in moderate outdoor temps never get cool enough to allow the stat to close.

 

So where is it above 160 degrees'

 

Simply as I can put it, in South Carolina where it can be 10 Degree's in January or 101 in July, all of my Builds Operate at the same Temp Range whether based on 180 or 195 Degree's @ 13 to 16 psi. any time of the Year, If your Vehicle will not do this you are lacking in you cooling System. The only Effect I've seen on Cooling Towers or Heat Exchangers are a Couple degree's either way on High Humidity, air being Saturated with Water. Never experienced this Condition with something as Small as a Radiator. To the Original Post, I hope you get it Tuned, Ignition Timing, Fuel Mixture @ Idle and Load, no Shroud, Transmission Tuning (automatic), Type of Fan Solid, Clutch or Electric Triggered all and more have to be optimum for Flawless Cooling System.

 

We all have our “opinions” on what is: not hot enough, just right, hot, and too damn hot. First I’d like my engine in the first 7-10 minutes to get up to where the thermostat opens. Second I’d like it to stay there for the most part. Next not go nuts in stop-go traffic with the AC on in the summer.

My engine is 67 years old and other than a valve seals and an electronic ignition all the parts or their replacements are that old. The 2 carburetors are 69 years old. Whether you like it or not the factory installed a 160-170 thermostat. 200 degrees even with a 7 psi on all the stock parts were #4.. too dam hot and the factories convinced us of that.

With the reconstruction/modernization of my car, a better radiator heater core, shroud, better fan etc. are now in it with a recovery system and I can use a 14 psi cap for more protection. At 190* I start turning things off eventho 230+ is still keeping the coolant on the inside. Modern engines can evaluate and correct and we know they can. Their metals, seals, gaskets if they even have any, can support the heat and the efi’s protect them. My 1953 WCFB’s can’t do a bleeping thing to protect my engine at 210* and neither can my ignition. “It is what it is” as they say they are getting ready to boil this s**t we call gasoline away.

If you want something to live at 210-220 do a damn good job of using what the factory did for it or install a EL-ESS. Yes I know many do live with their older engines running at a higher temp and that’s fine but it’s not for everyone.

 

Go back and re-read what @Blues4U said in post #53. The part of your post above that I have highlighted is a correct statement, but you are failing to see that it happens on both sides of the equation (heat transferred out of the system in the radiator and heat transfered into the system in the engine). The time/flow bit is somewhat self-cancelling in a car cooling system.......

 

Is it just me, or did you condenser grow up in the last pic?

 

Looks like 2 different installations to me. From what I’ve read the condenser and evaporator can be a lot smaller in a pick up.

 

AGELESS-- I am showing you 2 different pictures of 2 different builds full size condenser and a smaller size
works fine--the smaller one I used all rubber AC hose and located drier on inner fender--

 

Just fixed 2 overheating issues with an OT vehicle (F-150) I noticed the temp gage creeping up to 3/4 when driving in 3 gear over 2500 rpm. The truck had always been right at 1/2 gage reading for the previous 15 years. I opened the overflow/fill tub to check the coolant, but didnt get the cap all the way tight when I put it back on. Made the problem way worse, cooling systems need pressure. Simple fix, just tighten the cap dummy. But the needle is still on 3/4 mark. Changed coolant - no difference. Then I noticed the lower apron that funnels air into the radiator had torn away from one of the plastic fasteners. Stupid thing, probably hit some water and it tore the rubber apron.
I reinstalled the apron with larger fasteners and that fixed the issue completely. Temp gage is rock solid at 1/2 reading.
So 2 things - make sure the radiator cap and system are pressurized, and make sure there is no way for air to exit from in front of the radiator except through the radiator. If air can flow over or under or around the radiator, it will and you lose that cooling. And of course, get a well-fitting shroud for the fan.
Good luck!

 

This helps with a belt rubbing?

 

You mean added stress and making the engine work harder causes it to run hotter?

Must be it never got hot in Florida or people didn't dive before there was A/C in cars.

 

An interesting discussion with a lot to absorb. For an A/C car I happen to like a good quality electric fan, especially for when you are stuck in traffic or cruising at slow speeds at a show because the air flow is there when you need it. For your A/C to work properly it also needs maximum air flow over the condenser at low speeds. With an electric fan you'll also want to have a trinary switch installed in your system instead of a binary switch that will activate your electric fan when the A/C needs it.

From Vintage Air: "We should stop here and mention system protection switches. A “high pressure safety switch” disengages the compressor clutch on the compressor if internal pressure exceeds safe limits (406 psi) and then re-engages the compressor clutch when the pressure is back down within acceptable limits. A “low pressure switch” disengages the compressor clutch if there is excessive refrigerant loss (below 30 PSI). A “Binary Switch” incorporates both of these protections into one switch. A “Trinary Switch” incorporates both high and low pressure cutoffs, plus adds an “electric fan engagement signal” (at 254 PSI) feature to help bring internal temperatures down. These switches are great insurance on any system, and should ALWAYS be incorporated."

 

Myth.

Slow it down and your "heat generator" (engine) puts more heat into the coolant.

I apologize in advance for the following dissertation, but......

.....do a google search for Newton's law of cooling. The water moving too fast to cool is a myth. If you had a sealed rad (no flow) full of hot coolant, and subjected that rad to airflow, yes, the longer you left the coolant in the rad, the more it would cool. However, if you were to plot that cooling over time, you would find that the RATE at which the cooling takes place is an exponential curve that decreases with the temperature difference between the hot coolant and the air. Put another way - when the temperature difference (delta-T) between the hot coolant and the airflow is large, heat transfer (cooling) initially takes place very, very quickly (almost instantaneously). But as that happens, and the coolant cools, the delta-T becomes less, and the RATE at which further cooling happens gets less and less until the point where the coolant and air are almost the same temperature and continued cooling takes a very long time. This is Newton's law of cooling. The inverse of the above also applies, regarding the coolant picking up the heat from within the engine. The more coolant that you can move through the engine the greater BTU load you can haul per minute.

A good example of Newton's law can be seen when quenching a red-hot piece of steel in a bucket of water. At first, the temperature difference (delta-T) between the red-hot steel and the water is huge - therefore the initial heat transfer occurs at a great rate - the steel initially cools very fast - almost instantaneously. However, after this initial cooling, the delta-T is much smaller, so the remaining cooling occurs much more slowly. If you removed the steel after a second or two - it has cooled a lot - but it will still be warm. To continue cooling the steel to the temp. of the water, you have to leave it in there quite a bit longer - because as it cools - the rate of cooling continually decreases as well. In short - initial cooling is fast, but subsequent cooling occurs more and more slowly until cooling that last little bit takes a long time.

So what does this mean? Basically it means, the longer the coolant stays in the rad, the less efficient the cooling that takes place is - to the point that the rate of cooling is so slow as to be detrimental to overall system cooling. Better to dump the big load of heat right away and go back quickly for another load than hang about waiting for a last little bit of insignificant cooling to happen.

 

Amongst other variables, heat transfer is directly related to the temperature difference. In this case, that of the air and coolant (ignoring that of the surface of the radiator). In reality from a physics perspective the heat is transferred from the coolant to the radiator, and then from the radiator to the air. In heat exchanger design, one typically introduces the two fluids where the temperature difference between the two are the greatest to take advantage of that simple fact. Also, from a physics perspective, the energy absorbed by the air must equal the energy released the coolant - think of energy cannot be created or destroyed. So, in a way, the “system” always achieves a state of equilibrium. The heat transfer between the air and the coolant will depend on the mass flow rate of each, the heat exchanger design/ efficiency, and the delta between the two fluid temperatures.

 

I sure was!

 

THIS!!!! People, please stop posting the busted myth about slowing down coolant to improve cooling, it is wrong. Stop it. Thanks @Ebbsspeed

 

From what you wrote, I think we are in agreement. The key to the argument that water speed (as long as its fast enough) is irrelevant in its ability to remove the engines heat is that an uninterupted and never ending supply of water is being supplied at a predetermined desirable temperature.

Its not effective to slow the coolant passing thru an undersized radiator because in an enclosed system the coolant will also be slowed in the engine and absorb additional btus.........requiring even longer in the radiator.

Speeding the water up in the radiator and engine absorbs no additional heat and does nothing as each droplet of water would still spend the same percentage of time absorbing and giving up heat.

The point simply is that the area of the radiator must be sufficient to expel the btus generated by the engine . Even if you change the speed of the coolant, you do not change the percentage of time the coolant absorbs or expels btus for each minute it operates.

 

So you need a huge radiator to run no thermostat.

 

What would be the purpose of a high volume water pump? In what case would you need one?

 

To sell products. Like a high pressure oil pump for a street car

 

A thermostat is there to stop coolant flow only long enough for the cooling system to get up to operating temperature as quickly as possible. Once the system is at operating temp, the thermostat opens and has no further effect.

 

Yep and all I know is mine ran hot when I left it out
Stoped running hot when I put it back in
I ain’t no thermologist.
Ive only had a couple running hot issues ever. One was a stopped up radiator. One was the missing stat as a youngun another was a 180 stat that I replaced with a 190 (OE spec) and it no longer ran hot. Go figure.
Built tons or crap and fixed even more wrecks.
I didn’t know people had cooling issues on old cars (non track related) until I showed up here.
Without studying thermology, I’ve only had those 3 major issues. I guess ignorance is bliss.

 

As I mentioned before, if the coolant is in the radiator longer, this would mean the coolant is in the engine longer. The radiator dissipates the heat that is made from the engine.
Now I understand some have experienced “taking the thermostat out” and the temps increased, but I can’t get my mind around why.
Doe’s anyone know the flow of say a SBC stock water pump. And can it out flow a radiator? I/e if 5 gallons a minute (humor me) from the pump, can you put 5 gallons a minute with that pump through a radiator?

 

If the hot spots in the engine around exhaust ports and combustion chambers are so hot there's just barely some localized boiling there (nothing serious, just some small steam bubbles forming, and disapperaing once they mix with cooler coolant from other areas again - quite normal in a hot engine), removing the thermostat lets the coolant get out of the engine easier, reducing the coolant pressure inside the engine, lowering the boiling point.

Lowering the boiling point will turn that slight, localized boiling into far worse boiling. More steam bubbles in there prevent coolant from touching the hot metal, so the temperature goes even higher, more boiling follows and the borderline overheating you had is now more of a thermal runaway instead.

 

Another question, does adding water capacity help? I have a really long lower hose on my 250 engine to clear the fan blades, I probably added 1 gallon more capacity, does this help or hurt the cooling?

 

It should not hurt anything as long as its routing doesn't create a blockage.

This isn't directed at you, but rather as an explantion which should clear up a lot of misconceptions.

In a closed system such as a car has, the overall controlling factor is the ability of the radiator to exchange all the btu's that the engine can generate when operating under a high load or high speed and under any atmospheric condition.

In an effort to make this as simple as possible, lets discount all the things that vary, like type of coolant, pressure, speed, etc.......and just consider the interaction of the coolant to to the engine where it absorbs btu's and the radiator/air where it expels those btu's.

First the manufacturer must determine just how many btu's the engine can make when operating under worst conditions, and then add some for good measure.

For simplicity, we will assume that the temperature and humidity are never changing for our test. We'll use a common temp of say 90 degrees.

Now without using a fan or the airflow caused by driving, we must figure how much radiator area it would take to pass those max btu's to the air. It does not matter what speed the coolant is moving as there is no impediment in the system and coolant moves in a constant circle.

When the correct size radiator is used, the heating and cooling will exactly cancel each other when the engine is generating maximum btu's. It will balance out.

The temperature that it balances out at will basically be determined by the temperature of the atmosphere surrounding the radiator. If its 35 degrees it going to cause the engine to run colder. If its 110 degrees the engine will run hotter.

Operate the engine at less than maximum output and it will generate fewer btu's and the engine will still receive incoming coolant at the same atmospheric temp. I expect it will still operate at the same temp.

Speed the coolant flow up, and nothing really changes because its a percentage thing. If the water moves faster thru the engine, it also moves faster thru the radiator (which is perfectly balanced for efficiency)...........So whatever the ratio of absorbing/expeling is.......it does not change with coolant speed.

The problem with many systems is that they are not balanced well or there is no extra capacity available in the radiator. A system has the capacity to operate well under normal conditions, but when you push it a little further it is insufficient.

An optimal system is one that has more capacity to expel heat than its engine can generate under the worst conditions.

So how do we maintain an engine operating temp thats different from what the atmosphere allows in our simplified system? We incorporate an inpediment to the flow and we make this impediment controllable.........and call it a thermostat.

When your engine is cold, the thermostat is fully closed and water that is being pumped isn't circulated thru the engine. The thermostat blocks the passage to the engine and diverts the coolant to just flow thru the radiator.

As the engine begins to warm, the spring loaded thermostat creeps open and allows just enough water to pass thru that it maintains a specified temp.

IF there is insufficient capacity to cool the coolant as it passes thru the radiator, then the now wide open thermostat will pass the maximum amount of coolant, but it won't be cool enough to do the job.

To summarize: The whole idea of a properly working system is to have a radiator that has excess ability rather than marginal ability. It never hurts to have coolant stay in the radiator longer because the thermostat will contol how much of it you need.

Obviously radiators must work in conjunction with a fan to move the air and a shroud often can create additional flow that helps as well. Its nice to have a system that can operate at a higher temp due to a pressurized system, but personally I want that only as an emergency help.......others prefer to operate at higher temps. Thats their choice and I respect it.

The point simply is that one must have a system that is not operating near its limit during normal driving conditions because there will always be traffic jams and hot weather.

 

Howard Stewart had some good info on cooling systems.Basically he said radiator should be cross flow with the rad cap on the other side ,so peak pressure coming out of the top hose won't push the cap valve open,Street applications, the water pump speed must at least match crankshaft RPM, to a maximum recommended 25% faster than crankshaft speed For cooling systems NOT using a cross flow radiator, mounted higher than the engine, you must use a surge tank. A surge tank is typically a 1 quart tank mounted at the highest point of the system, with the radiator cap on top. Any aftermarket thermostat housing that mounts the radiator cap directly above the thermostat location, or that mount the radiator cap in the top coolant hose, are NOT recommended. Both of those housing styles are poorly designed, and will push coolant out of the cap at high RPM.

 

So, why do engines have a water pump at all? Coolant will flow through an engine without a pump. I've seen vintage equipment that had no water pump at all, the water flows purely due to the action of hot water rising up and out of the engine, down over an open screen and into a pool. As the water moves up the engine due to heat it draws in cooler water from the pool at the bottom of the "radiator" screen. The engines run fine like that, the water cycling in and out of the engine with no pump to move it, and back in the day when they were new they would wok an entire day out in the field plowing. If changing the rate of flow has no effect on cooling system performance, than why have a pump at all? Something tells me your theory doesn't hold water.