Technical New AC…and now SBC runs 30 degrees hotter

I'd start with a shroud and Water Wetter. I'd all but guarantee those two things alone will drop your coolant temps 10 degrees, if not more. You can also consider going to a larger fan with more blades, without a clutch. Also, if you're running at 195 on a 90 degree day with the A/C on, and the engine is holding that temperature at idle, in traffic, and running at speed, then in all reality, you're concerned about a problem that you don't have. The temp is going to be higher with the A/C on. It just is, and that's to be expected in normal operation. I don't see anything wrong with some overkill measures when it comes to cooling, but you also don't need to fix things that aren't broken. 195 is a perfectly reasonable temperature for an engine, especially if you're holding it, and not passing 195 on the way to 220. I'd much rather cruise at 195 and be comfortable in a nice air conditioned interior than running at 180 while sweating my balls off.

 

Shroud it. My 57 ran 200 all the time, then I put a Danchuk shroud on it and it settled at 185 even in the SoCal desert heat. My 56 Imperial ran a 195 Tstat and had factory air with a big factory shroud. It ran 195, always and forever idling in the pits of hell itself. 210 doesn't seem bad at all. Try a bigger T-stat and a shroud before making any other mods.

 

Humm--if that's the case with no tstat, i wonder why Detroit keeps putting them in cars-it must cost a lot of money for like a few million tstats. True, a restriction does slow the flow-that's the point. The purpose of the radiator is to cool the liquid, flow it fast and the cooling efficiency falls off dramatically, slow it down and it cools fine. Tstat also allows a set temp for maximizing fuel usage and performance (210 on most cars today). A viscous clutch fan operates full bore at idle an low speeds, slows and drops out above a speed that is sufficient for the radiator to cool the motor-thus saving hp and fuel.

 

just a couple of notes (i have a 55 also w/ homebuilt a/c):
--looks like orig. 55 rad..have you had it flushed/cleaned-like ever? Keep it though, its a good one.
--pressure cap-rating? i've been told 14 lbs. is average. That's what i use.
--hard to see pix, but how far is fan from rad.? 1", maybe a little more is good.

 

Probably the main reason Detroit puts them in is so the car will have interior heat. As for a old style clutch fan they slip all the time. Then the older they get the more they slip. His cure could be as easy as removing the thermostat. But then he really may not have a problem. That just might be what the car runs.

 

There is a difference in fan clutches, regular, heavy duty, severe duty.

https://www.4s.com/media/3747/4s410-fan-clutches-standard-heavy-severe.pdf

 

And once the temp reaches 200° & thermostat stays open ?

 

Careful with pressure on the tri five original radiators. They will not like the pressure. Seam are not made for it. Dan chuck shroud works. Six are seven blade fan will help. Making sure the radiator is in good condition. Lower radiator hose may be collapsing also.

 

If you run no thermostat, you need one of these:

And you need to read what @ekimneirbo said above. I didn't hear that on the internet. I learned it at machine shops, building engines. Mike

 

So why do you need to run one of those and which one would you use ?

 

They are for race cars…mostly circle track.

 

From your pictures, I would guess your problem might be related to the lack of sealing over the top of your radiator/mounting plate. A HUGE amount of air may be cruising right over the top of your radiator even with the hood baffle if it's not sealed. How about a picture of the underside of your hood. There should be a baffle with a notch in it to clear the radiator hose connection in the center (the 6 cylinder radiator hose location is different... BUT you can improve the sealing by fabricating a rubber "dam" or maybe even a split foam pipe insulation onto the bottom of the hood baffle, or on the top of the radiator mounting plate... when I sealed mine up, it made a world of difference...

 

Having studied-and passed multiple exams-in heat transfer, I have never been able to accept the idea that cars without thermostats run hotter because “the coolant is passing through the radiator too quickly.” Heat transfer (on a btu per hour-sq. ft -deg basis) almost always improves with increasing fluid velocity inside a tube.

But I don’t doubt the experience reported by many that a car can run cooler with a thermostat than without. What I think is actually happening is that the cooling system without a thermostat, due to lower frictional pressure drop, experiences cavitation at the water pump inlet. Remember that manufacturers design water pumps for the system resistance with a thermostat present. Cavitation occurs when the local pressure is less than the vapor pressure of the fluid, producing vapor bubbles that limit the pump’s ability to pump. Those bubbles collapse at the pump outlet, so aren’t readily detectable. The cavitation actually reduces the total coolant flow through the radiator, thus enabling overheating. Overheating doesn’t always occur without a thermostat, because if a vehicle has a large enough radiator, it can cool adequately even if the flow is reduced.

 

The opening event is True but recircling water at 180 is a Hell of a lot differ from than at 195, it's easier to pull 15 degree's out of water than 30, I would swing for the Fence with 195 on a Bigger Rad. AC load shouldn't be causing a 30 degree difference, something else is going on. What coolant mix are you running, are you sure there is a Good water pump.

 

Been in the Chemical Industry and Manufacturing of Chemicals for 30 Plus years, this is the Dumbest statement I have ever Heard, Heat Exchangers and Radiators are Directly associated with Flow and timing in Removing BTU's. Try working in the Field and quit taking exams

 

We've put the "you have to slow the coolant down to give it more time in the radiator " several times before, but it just keeps coming around. Stop it guys, you're wrong. The faster the coolant flows, the more cycles it makes, the more heat is removed.

 

I suggest that folks remember the cooling system on an automobile is a "closed loop", a recirculating closed loop driven by a mechanical pump. In this type loop, the time element is crucial for the fan to pull air over the fins and coils and cool the liquid-i.e. heat transfer. A restriction fitted to this type system allows the max cooling that can be achieved by the radiator-which of course radiates the liquid's latent heat. In an "open loop" system, say a water hose flowing water through the motor and out, the temp can be controlled by the inlet water temp. Yes, a larger radiator (bigger tank as above) w/out a restriction will cool its subject, providing the "subject" generates a nominal heat load.
Tstats are used for a variety of reasons, not the least of which is overall size of the radiator for the vehicle it is intended.
But, many swear this is not the case, w/out is the solution. Before those dammed rockets, i just knew the earth was flat.

 

At road speeds, she seems to hold around 190. Idling in traffic 210ish

 

I quit working in the field 6 years ago at the age of 61 after spending 40 years in power generation, heat exchanger design, and system design. But feel free to believe whatever you want.

 

I dabbled a little in heat exchanger theory when we started manufacturing our own copper tube/aluminum fin coolant heater, evaporator, and condenser oils. Essentially all the same physical construction, but different fluids (gas/liquid phase(s) in evap and condenser) vs liquid (single phase) in coolant heater. It actually gets extremely complex in terms of the math, and hence the introduction of computer modelling which has it limitations based on many assumptions. At one point we were asked to manufacture an oil cooler for a military vehicle hydraulic system. We had no clue, and hired a “consultant”. A mech Eng who had extensive design experience in heat exchanger design and fluid mechanics. He came up with a piece of twisted stainless steel that was fed inside the 3/8” OD copper tube. The prototype was tested and didn’t perform anywhere near the “predicted” performance. The idea was to “slow” down the oil and to cause turbulence to increase heat transfer. At least that is what I think it was all about, but it was over 25 years ago. More prototypes and more of less than predicted results. Big problem. We hire another “consultant”. This time a guy with a PhD in thermodynamics. Turns out that the twisted piece of stainless steel wasn’t making enough actual physical contact with the inside walls of the copper tubes. It looked and felt as though it did as they were inserted, but not in reality. I think a lot is still really unknown when it comes to these complex scenarios that even advanced modelling doesn’t quite capture, but I have been out of this arena for too long, so I cannot say for sure. I will say, this book was the best I ever found on the subject, and I kept it all these years later.

[edit] All this talk just jogged my memory, and for “extreme” performance evaporator and condenser coils, we used to purchase copper tubes that were internally “rifled” in a manner with very fine spiral ridges. Again, the purpose of this was two-fold to help increase heat transfer performance. One, it caused the fluid/gas to mix a bit better. Two, it increased the inside surface area in contact with the fluid/gas slightly. It think overall it “only” offered a 10-15% increase in performance, but in some instances where space was at a premium or airflow could not be increased, it was just that little extra that was needed.

 

I'm at the ball game right now, and I'm not going to sit and type out an essay on my phone, but to the guys that think you have to slow the flow rate to give the coolant more time to give up heat in the radiator, your theory has a fatal flaw, slow the rate of flow also keeps the coolant in the engine longer where it picks up additional heat.

 

Can slowing down the fluid/gas in a manner which results in greater turbulence/ mixing of said fluid/gas provide a net gain in the overall heat transfer coefficient?

 

Apparently, you either didn't read the entire post or don't understand cavitation. I believe his point was that without some back pressure on the water pump at higher RPM could definitely cause pump cavitation which would essentially reduce the flow overall. In addition with a thermostat and a restriction at the outlet of the engine raises the pressure inside the block which also raises the possibility of boiling at hotspots which also reduces heat transfer at the surface interface between the block and the water. His posting and theories are entirely reasonable. Try not to be so judgmental... Especially considering your admission of a lack of education.

 

Does slowing a liquid result on turbulence? Or does increasing the flow rate induce turbulence? Look up Reynolds equation.

 

That’s not true at all. A thermostat regulates engine temperature, just like a thermostat at your house. Engines have an operating temperature for peak performance, and the thermostat is one of the things that help regulate that. A no-heat complaint due to a stuck open t-stat would only happen in extreme low temps, if at all.

 

Thanks for mentioning the Reynolds number. It had long faded from memory, and I just spent too much time reading up on it and my brain hurts. Brings back my university days. I was thinking within the context of altering the internal geometry such that the flow pattern is changed to turbulent flow vs laminar flow. I think we can all appreciate that increasing the flow of a fluid can induce turbulence, and we can also appreciate that heat transfer can be increased by mixing a fluid. This is common sense based on what we can observe everyday. So within the context of my oil cooler example, and the addition of a “mixing” device, is the fluid velocity increased or decreased all other things being equal? I, myself am having trouble grasping the correct answer, and I not trying to be a smart ass.

 

No kidding, I’ve heard this repeated so many times I just shake my head.
If folks who think that “leave the coolant in the radiator longer” allows an engine to run cooler, what do they think is happening to the coolant in the block?

 

The purpose of a Tstat is to keep the operating temperature up. When it closes down, the coolant is now in the block, or flowing out of the block at a lesser rate, while the coolant is in the block it is heating up.
When the Tstat opens fully, more, etc, now more flow is occurring into and out of radiator, cooling that fluid down.
If I had a guess, anyone who had an issue, or who’s friends, brothers uncle etc did, that caused an engine to run hotter without a tstat, probably had the lower hose collapsing and just never saw it or noticed it.