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Radiator swap Aluminum to brass.

JiFaire said:
But after all that, probably the biggest thing was driving savvy. I would get into a 6* hill in 100* ambients in Utah and pull in 3rd (TC locked) at 48 mph all day. If I tried for 55 mph, I would overheat. I knew that, so I quit doing it. If the wind was in my face, the same thing could happen. I pulled that high-front 5er all over the western US with no problems because I watched the gauge and drove by water and exhaust temps.

Before all that, the damn thing almost overheated with the engine off ... for damn sure, I never tried to pull even little hills with the AC on... I would end up on the shoulder, crawling along at 25 mph, trying not to blow up.

All the little things add up - everything contributes. Changing the rad, adding a Kennedy clutch, using WMI, or installing a SSD 180* Tstat isn't going to magically cure the problem, despite the hype and the claims.
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Well, yes, you can get out and push. :D

Now if you want to get all you can out of your 6.5 and climb the hills without the flashers on it will take every trick in the book. Getting the fan on soon, HO pump, and low temp stats stop the heat rise before you get over the 210 mark even in AZ. Airflow is the biggest problem this body style has - even GM addressed it with the 20" 9 blade fan.

I agree - Weak fan clutches or plugged radiators (also corroded and internally plugged) just can't be overcome by something else.

Ron Davis, racing radiators, will not build a thicker radiator for the 6.5 - because they tried it and it made no difference. So yes there may be a difference between them, but, if the airflow is not there a thicker radiator will not help as the air is as hot as it will get before it exits the core...

Airflow through the radiator appears to be problem #1 with water pump flow issues being #2. This includes the thermal delay (airflow) before the fan clutch can lock up with the sudden onset of a hill and full power.

The aluminum radiator I got from Performance Radiator and used in my 1993 did the job well. My 1993 has all the bells and whistles for cooling except dual stats. HO pump, low temp Kennedy clutch, Water wetter, 9 blade fan, 180 t-stat...

This is biased on pulling a 28' on 10% grades in AZ temps where the sound of a working fan is a comfort not a fuel sucking annoyance because the alternative is scuffing the pistons or cracking the heads if not caught in time. Your use may be different and not require every trick...
 
robzombie4551 said:
That's the heat carrying abilty, not the heat transfer ability. Look at aluminum s # and the coppers #.

Almost twice the heat dissipation of copper. Aluminum asbsorbs/transfers more heat and as a welder in school, ask your instructor which dissipates heat faster aluminum or copper, brass which is copper and tin combined is a little better than copper, at heat transfer.

Or do this simple test heat a piece of aluminum and a piece of copper, same thickness and see how long it takes each one to reach the same temp with the same amount of heat applied.

Please let me know what he tells you as I'm curiuos as to the answer he gives you.

I'm not sure you're interpreting your book properly.

Brass will definetly last longer than aluminum, but the MFG. use it for weight savings as well as being more efficient.
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Been a while since I was in school. If the numbers you a referring to are from the link I posted then every metal listed below al. would have better heat transfer.

We'll just have to agree to disagree.
 
Acesneights1 said:
I may try the Kennedy clutch this time around since my burb has the 4 bolt.
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If you want ... but you might talk to Oregon Horse Tug or Turbine Doc before you go there... the Kennedy clutch kicks in way to early and stays on past the point of common sense. I had a 4-bolt Heath clutch in mine, and I didn't change the fan, either.

There is a whole science behind the clutch application... it's more than merely SD or HD. Lots of guys have tried the GM SD clutch (because it's cheaper than the Heath clutch) and just not gotten the same results.

It's about kicking in a bit earlier, but it's also about torque transfer... the rpm loss through the viscous fan clutch. The way Bill explained it to me, his fan loses less than the GM one. There's lots of documentation on it on the web. You might also try pulling yours, cleaning the coil, and doing the mod on it, before you go spending a bunch.
 
I didn't address the "absorb" vs "dissipate" conjecture. I think that's related to how much heat a given material can hold. Here's another link:

http://www.ami.ac.uk/courses/ami48 [...] up_02.html

aluminum = 0.896 kJ per kg per Kelvin
copper = 0.383 kJ per kg per Kelvin

It appears that aluminum is the clear winner at storing heat, however the table shows specific heat in terms of mass. We know that copper is a lot denser than aluminum. We are probably interested in comparing a given volume of aluminum vs the same volume of copper, so gotta convert the table to volume instead of mass.

Here is a table of densities for various materials:

http://www.mcelwee.net/html/densit [...] rials.html

aluminum = 0.002643 kg/cm^3
copper = 0.0089 kg/cm^3

multiplying by these factors,

specific heat of aluminum = 0.00237 kJ per cm^3 per Kelvin
specific heat of copper = 0.00341 kJ per cm^3 per Kelvin

so by mass, aluminum is better at absorbing heat. But by volume, copper is the clear winner. Given that we are usually space-constrained inside an engine compartment, copper would be both better at absorbing heat and dissipating it. Sorry I had to run you through this calculator exercise, but i couldn't google up any webpage showing specific heat in terms of volume.

Copper and aluminum are both effective materials for rad. construction, but they have different requirements. If you want to know why, consider a great chef's kitchen.

Aluminum sure can move heat, if it has been done right. It very efficiently absorbs and transfers heat to it's environment and things that interact with it. This works great for bacon in the morning, and even for boiling water, but isn't so good for a large, thick filet mignon. That cold slab of beef sucks the heat right out of the aluminum, and there isn't any left to keep up the cooking. Many people who buy aluminum cookware have a lot of trouble doing steaks properly for this very reason. Aluminum has a low thermal capacity, and a very high thermal conductivity.

As such, aluminum just wicks heat away with little concern for anything else. It won't wick as much as copper, but it sure will move it quickly; Dumping it's capacity as soon as any heat leaves the rad., and quickly soaking up more.

Copper moves heat as well, even if it hasn't been done all that well. Copper very efficiently absorbs and transfers heat as does aluminum. It does it faster, as well. That said, copper has an incredibly high thermal capacity. That big fat steak just can't suck up all the heat that copper will hold on to, and this is where copper and aluminum differ in requirements. Copper won't readily dump all the heat energy it picks up, because it holds so much of it before it changes temperature to any great degree.

That leaves us with a problem. Copper needs help. Somehow, you have to remove all that heat from the copper, as it will just hold on to it otherwise. A copper rad. can work much better than an aluminum one, but you have to either have loads of cores and lots of fins and airflow.

The thermal capacity of copper, when compared to an aluminum rad. of the same design, completely removes the benefit of using copper in the first place without help. As a matter of fact, a poorly designed copper rad. can be much worse than an aluminum model.

The best way to use the materials is being tried nowadays, and that is combining them. As with most good things, they work better together than apart.


How about we're both right. I think you're right that copper absorbs heat faster but releases it slower. Air moving over aluminum will dissipate the collected heat faster,as copper wants to hold on to it.
 
Yeah, but it isn't just about holding the heat, and that's why specific heat capacity isn't the measure you want... it's about moving the heat, and that means surface area, which your post alludes to when you talk about fins, more cores, and airflow.

The biggest problem is that air is lousy at absorbing heat, and it takes a bit of time to hit capacity. That's why Heath's big ugly slab of aluminum works better than some of the other PMD coolers with fins. Surface area and mass. The aluminum plate surface can radiate the heat faster than the PMD-cooler interface surface can absorb it.
 
It's robzombie. I'm on the laptop.

The biggest problem is that air is lousy at absorbing heat, and it takes a bit of time to hit capacity. That's why Heath's big ugly slab of aluminum works better than some of the other PMD coolers with fins. Surface area and mass. The aluminum plate surface can radiate the heat faster than the PMD-cooler interface surface can absorb it.
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Yes but there is no hot liquid in the heat sink. Only air passing over a solid chunk of aluminum. Different comparison altogether.

I'm no engineer and not trying to start anything here. I'm just reading alot and from everything I've read aluminum is better for a thermal transfer from an internal prospective.
The aluminum is hot from the coolant INSIDE, and the air outside passing over it pulls more heat away from it than copper of the same density and mass.

Sorry for confusing you with the different names.
 
Kenny, the 92-93 6.5 trucks had a factory copper radiator, you might try one of those. They had the cap on the radiator though, like your 6.2. I think the copper works better if the price was the same, I dont know if they work so much better that it justifies the cost over aluminum though.
 
Just thought I would throw this in, seems self explanatory.
 

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UNCLE.

Copper retains the heat/cold much longer . evaps. made of copper

Aluminum rejects it,carries it away faster. condensers made of aluminum

Both materials are used in those respective parts of the system due to the efficiency of their properties.

Your're right and I'm wrong?

You win I 'm done disputing this. I really don't care as my truck doesn't have overheating issues since I installed the ho W/P and new rad. and now I can tow in 100* plus with ac on and no issues.

I guess I can't believe everything I read.
 
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I just Re-read that article you posted and as I read it, it backs up what I have been trying to say, heat travels faster in aluminum, copper is excellent in chill strips.


Thank you for helping me prove what I've been reading all along.
 
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Metal [Material] Symbol, Atomic Thermal Value
Silver Ag 4.08
Copper Cu 3.94
Gold Au 2.96
Aluminum Al 2.18
Beryllium Be 2.00
Tungsten W 1.74
Rhodium Rh 1.50
Molybdenum Mo 1.46
Chromium Cr 0.937
Nickel Ni 0.92
Platinum Pt 0.716
Tin Sn 0.666
Tantalum Ta 0.575
Lead Pb 0.353
Titanium Ti 0.219
Manganese Mn 0.078
 
I thought one of the biggest problems with the 6.5 is there isnt enough airflow through the engine compartment. I would think a body lift would help or a cowl hood.
 
midniteplowboyy said:
Kenny, the 92-93 6.5 trucks had a factory copper radiator, you might try one of those. They had the cap on the radiator though, like your 6.2. I think the copper works better if the price was the same, I dont know if they work so much better that it justifies the cost over aluminum though.
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Yeah I saw that actually in Summit's catalog. Like I have said I would not go out of my way on this but I will have a spare rad to test on. I would not blow 3-400$ on a rad just to "test" a theory. The rad coming out of the CUCV has a minor leak where the heater hose goes in so for about 35$ I can have it fixed and cleaned and will save it for sping for comparison when I pull the Burbs rad for spring cleaning. Truth be known I'll bet the 92-93 is the same one in the OBS. Probably the 88-91 NBS had Brass as well IIRC with the 6.2.
 
What would be real great is a 3 3/4" core radiator with copper tubes and aluminum fins.

Copper absorbs heat better, but it holds it, cannot reject it. Aluminum loses heat much faster. So the best heatsinks will have a copper core surrounded by aluminum with aluminum fins. Then you have copper absorbing the heat from what you want cooled, but a much larger surface area to transfer it to the Aluminum which can shed it to air much more efficiently. And more smaller cores would equate to more surface area for water to touch.

All copper is good if you have a lot of surface area and a lot of airflow constantly to disipate the heat, but then your fan would have to be engaged a lot more. So not only does copper cost more, it requires more space and more weight unless you have more airflow, like a direct drive fan that most old big engines had.
 
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