Technical New AC…and now SBC runs 30 degrees hotter

As for overheating w/o thermostat, it's not a matter of how fast the water moves, it's a matter of the pressure (in different parts of) the system. The restrictor plates in your picture gives a pressure increase inside the engine as it doesn't let water out easily, bumping up the boiling point. With no restriction coming out of the engine hot areas such as combustion chambers and exhaust ports may have localised boiling, even if the general coolant temp is far below the boiling point. Steam bubbles reduce contact between coolant and metal, and you may soon have a thermal runaway on your hands. Confusing that you can make an engine boil worse by removing the thermostat, but the laws of physics are there, explaining it.

I can see it's easy to confuse this with it being caused by water moving faster when unrestricted. One of those cases when people have seen a problem and figured out an explaination that seems to fit the facts, but not enough facts are taken into account so the end product is wrong.

 

Apologies if my post took this thread away from addressing the OP’s problem.

One thing I didn’t see mentioned is idle speed. When you engage the A/C clutch on a carbureted engine, engine speed (thus fan speed and water pump speed) are going to drop due to the power consumption of the compressor. IIRC, back in the days when all all cars were carbureted, at least some of them used a solenoid to bump up idle speed when the A/C was on. Nowadays with EFI, that’s handled automatically. Since the OP’s concerns are at idle, checking idle speed with and without A/C may point to a remedy.

 

From looking at your pictures, I would suggest getting some heavy cardboard and some Gorilla tape and cobbling up a temp shroud. Tape some vertical pieces to the side uprights. Then bridge the top with a curved piece of cardboard or thin sheetmetal. Maybe something on the bottom side if there is room....and see if it helps any.

 

I hope every car (non flathead anyway)I build runs 210 in the summer time with the AC on.

 

So, a Thermostat was just something they pulled out of their Ass for Shits and Giggles.

 

Eewwwww, that's nasty!

T-stats are used to get an engine up to temperature quickly by restricting the flow of coolant out of the engine block, keeping it in the block where it will heat up; not to improve the cooling performance of the radiator by keeping the coolant in the radiator longer. If that were the case there would put it at the outlet of the radiator!

 

With regard to overheating without a thermostat,

Tech Tips #3 at
www.Stewartwaterpumps.com/

(Sorry I was unable to post a link directly to the article, but there’s a link at the top of their homepage to their “Tech Tips”)

offers another theory, which I believe is based on dyno testing by Howard Stewart, that without a t-stat, the inlet side of the radiator sees a higher pressure which can overcome the radiator pressure cap’s spring, causing loss of coolant with resulting overheating. The article says newer cars became immune to this by using cross flow radiators where the cap is at the outlet of the radiator, thus seeing lower pressure.

 

You hit on the "crux of the problem" perfectly when you said that slowing the water in the radiator also slows the water in the engine. Yes thats exactly right and that is why the speed of the water thing doesn't "hold water" .......so to speak.
In my earlier post I mentioned that speed of the water is not a factor as long as you have an unlimited supply of water at the correct temperature. In an enclosed system, thats what you have ONLY when the radiator can supply it.

If your radiator is not capable of supplying water at the correct temperature, then slowing or speeding the water doesn't really matter. The radiator can only transfer as much heat as the air around it can absorb. More air more heat absorbed. Less air, less heat absorbed. The air does not care how fast the coolant is passing thru the radiator.

 

I ain’t no scientist either.
T-stats maintain the engine operating temp the engine designer wanted. The radiator, fan and shrouds were designed to cool/maintain that operating temp.
I don’t over think this crap.
hoses, stat, pump in working order my trouble flow chart kinda goes like this:
Runs hot a idle but not cruising? Probable got sufficient air or coolant flow at idle. Needs more air flow at idle Causes for idle hot issues are usually bad air flow when stopped. Crappy fan, no shroud.
Runs hot cruising? Probably need more radiator.
What is too hot?
I guess that depends on the engine sometimes. Older flat motors generally need to run cooler than OHVs in my work experience.
I’m used to working on cars where fans might not come on until 215-220 ish.
Cruising on a hot day with the AC on and run 225-230 without issues.
For performance stuff, I use the cooling scientists at a radiator manufacturer. Those guys are smarter than me.
They ask goofy questions like engine size, HP, gvw, AC……they enter theses answers into a massive data bank that spits out the core size area needed to cool it. So far so good on my method.
Why did my SBF run hot with a 180 T-stat but not the 195?
Don’t know. But anytime I pick up a t-stat at the store I always start off with the temp the factory recommended now. So far this theory has held up well.

 

You should have told that to Cummins when they engineered their low flow cooling package. The coolant flow was slowed down and the radiator was made a multiple pass. It was a band aid they used before going to electronic injection. But it allowed them to closely control engine temperature and keep it at the optimum point for emissions. They kept the coolant in the block and radiator longer for maximum heat exchange. They controlled the temperature with dual thermostats.

 

Leaving out science, sort of. This sure looks like OP has a factory 6 cylinder radiator. Anyone care to guess how many row's they have?

 

Or just using the 6 location for that front runner system.

 

Look at the radiator carefully. One just doesn't move it fore and aft at will.

 

Nope. Some hood baffle/brace interference.
That rad looks to have a raised inlet to clear the core support.
But v8 rads are available to run in the 6 position.
Is this one?
The owner probably knows.

 

One has to look at the back side and see how far back rows are set back from tank because looking at side profile will get you no where. There is one other baffle you didn't mention.

 

The Cummins Low Flow Cooling System is a very complicated system which can be studied here: https://www.freepatentsonline.com/4520767.pdf

If you read that entire description you will not find that the flow of coolant was intentionally slowed down to optimize cooling. You will find that the system used a lot of logic to compare temperature differentials and direct the coolant in different directions depending on the ▲T. It appears that the coolant was also directed to the bottom of the radiator and forced up to the top where it was then redirected back down to the bottom and back to the engine from there. Cat also used such a reverse flow cooling system. I think introducing these systems which have almost nothing in common with a vintage passenger car, or traditional hot rod, cooling system just confuses the issue.

 

The radiator is a 4 row. I have a foggy memory of buying it ....36..37..years ago? This was a V6 car when built, but I found the rad support on an abandoned 55 in the woods of SC 30 years ago. The previous support had been hacked an used angle iron for the top rail. I moved the rad up front after moving to a long water pump and relocating the engine and inch or two forward to make room at the firewall for an HEI. The rad bracket is a homemade "whatever it takes to make it work" setup.

 

That explains why it looks near factory. How you got it up front isn't my point here at all. Maybe I missed a comment stating it was a 4 core unit mention here prior? The simple matter of my question was aimed only toward the capacity of the radiator.

 

Ya did good.
I haven’t got to that point on my 56.
I’ve got all the long water pump pieces I need. But close on having the short water pump parts as well.
But I got a small cap electronic dizzy to fix the clearance issues.

 

When I bought my current Delray it was a I6-Powerglide. I took the radiator to a local shop who had a '55 V8 radiator that they had rodded out. I had them remove the I6 radiator side mounting plates and soldier them to the V8 unit. Maintaining the six cylinder position. The stock V8 radiator cools my 292 cu in small block with the addition of a shroud and six blade fan. Averages 180 all day from 70 to 100 degrees ambient. It's no secret that the cooling system needs to be balanced with the correct components. Thermostat, water pump, shroud, fan, etc. If I ever add ac I expect the temp to rise 20 to 30 degrees. It's important to remember that once the car reaches 25 mph or more and it over heats the fan is not the problem.

 

Here is a magazine article which was written when a radiator was needed for a 55 Chevy......... Notice what it says about the cooling points that actually transfer heat to the air.

 

Cool article!

 

Mark, yours would be the first instance I’ve ever heard of with that occurring (first hand)
I’ve had to pull a few thermostats before in old radiators and also crossflow radiators, all vehicles ran 140/145 at speed.

Now I do succumb the the theory that coolant flowing too fast through the engine could cause pockets of air due to turbulence, etc, but I’ve never seen it on the gauge.

 

210 degree's is not hot, it's actually close to the optimum temperature for performance and efficiency. Just had my heap out today in 100 degree heat and it never got over 200 degree's.(190 degree's, according to the Stewart Warner mechanical gauge) That's at 60 mph at 3200 rpm's with a 4 row Desert Cooler radiator, a clutch fan, and a fan shroud, at 10 psi. If it get's to 230 or more, that's a problem. That's with NO thermostat or restrictor...

 

If you had space, you could always mount a heater core up in the front fender and plumb the heater hose to it, that would get rid of heat and add water capacity.

 

There are lots of ways to look at whats the best or most efficient. I agree that engines probably tend to burn their fuel with more efficiency at the higher temp, and I believe it helps with emissions as well.

The thing to me is that the basic medium that we use is water and at just 212 it boils and turns to steam. We increase that somewhat by adding pressure to the system and anti-freeze to the water.........artificially raising its boiling point. I tend to be willing to give up a little of that efficiency to be further below that 212, so that when something does happen I have more of a cushion before its a problem.
Also, higher operating temps are harder on components and push an engine closer to pre-ignition, and with the variations in todays fuels, you never know for sure what you are getting.

I agree with your comments but think that I would rather have an engine that operates in the 180/190 degree range. Lots of peoples engines operate satisfactorily at the higher temps. The question always is about when someones engine operates at the specific temp they want.......is their system already doing the maximum it can and just getting by, or does someone have a system that easily maintains that temp and is not being overly taxed to do so. So a temp that normally never gives one person any problem, may be the same temp that is operating on a thin margin for someone elses system.

 

My set-up contender in front of 3 row aluminum radiator with CORRECT shroud and fan with AC

 

Last word, "problem". The only problem I see is how people view their temp gauge and assume they have a problem. Today's car's with it's computers have been brain washed (programmed) to only see a problem. It's known as artificial intelligence. This facet of intelligence ignores all that is right and corrects only what is wrong.
So if OP's car isn't throwing out water or having issues why is old school thought (programming) of where temp needle should be playing a part here?

 

Had a newer vehicle that ran perfectly but kept setting a trouble code. The problem as far as it was concerned was that my thermostat was simply taking slightly longer to completely open than what it felt it should. Guess it was an emission thing rather than an actual cooling issue because there was no discernable issue to me. Still I had to install a new thermostat or be annoyed by the light.

In my older vehicles, I (arbitrarly)define a cooling system problem as being anytime my guage exceeds 200 degrees or is leaking fluid.......
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