tkheld

This appears to be a common topic now that everyone is driving in the hot summer months.

Can anyone explain how to determine an engine's cooling requirements and how that translates to the type of radiator required?

The options out there are confusing. There are aluminum radiators, radiators with plastic tanks, you can opt to have the old one re-cored, there are 2-core, 3-core, 4-core options, fins per sq inch, size of tubes, etc.

I would prefer to avoid guessing at the best performance vs cost on the various options on the internet and make an informed decision.

I have a 67 Cutlass with a stock 330. I am sure the radiator is the original - it's been in there for 47 years and who knows how many miles. I have no idea what it's current cooling capacity is.

What I do know is that after running the engine for about 15 minutes, you can't get near anything under the hood without burning off some skin.

It would be great if someone could weigh in with a little Radiator 101 or post a link to site that can explain this topic for those of us who are not very knowledgeable in this area.

Thanks,
-Tim

oldcutlass

Well the burning skin part is normal with any cast iron engine. Are you having temperature issues with you engine? The skin sizzle test is about as accurate as the butt dyno, just saying.

tkheld

Ok - Ha Ha - that was a pretty dumb comment. It burns when I put my tongue on it too.

oldcutlass

Lol, I suppose it does. The radiator has absolutely nothing to do with whether a hot engine will peel your skin or not. The standard operating temp of an engine is 180 degrees and can go as high as 215+.

So the question is what temp is your engine actually running.

ankerclanker

I have asked before about cooling and was told that about 190degs was
normal for my 330ci. I still feel this is a bit warm for a small block and have
done a few things to try and cool my engine down a bit. Cant answer your question about radiator size fins, rows etc. I put a 3 core aluminum radiator, 160 thermostat, built a shroud and added an electric pusher fan. engine
still runs 190 to 205.

oldcutlass

Those temps are not bad, right in the normal range. As has been explained in the past, a thermostat controls minimum operating temp, cooling system effectiveness and outside air temp controls the max.

ankerclanker

thanks Eric, I have the feeling that I am just a bit cautious on engine temps.
guess the thing to do is not stick my fingers or my tongue on the engine after running it and relax about the temps. thanks again


ted

olds 307 and 403

I had a 3 core rad in my Cutlass, cooled about the same as your car. Get a temp gun, double check your temps. I have a feeling my gauges read 10 degrees high. I am going with a Griffin 2 core, the 3 core is in my Olds powered 4x4. It runs cooler in it for some reason.

jaunty75

Remember, it's just as bad for an engine to run too cool as it is to run too hot.

In my opinion, when in doubt, the book prevails. If you're looking to replace the radiator on your stock 330, why not go with a radiator identical to what was in there, and go with a thermostat the same as what was in there originally as well? The designers of the engine chose the particular radiator, thermostat, etc. as well to work together as a unit. If you go changing things for no reason other than a "gut feeling" that the temperature isn't where it should be, you'll likely end up doing more harm than good.


As oldcutlass notes, an engine running 190 to 205 is absolutely fine, and people should stop worrying so much about this. If you get above 220, I'd be worried, but otherwise, no.

redoldsman

Remember, it's just as bad for an engine to run too cool as it is to run too hot.

Not to start an argument, but I guess I would disagree with his comment. I don't know that I have ever seen an engine run too cool. I not saying it doesn't happen but I have been around a few years and have never seen it. These are just my opinion and experience.

jaunty75

An engine that runs too cool experiences incomplete combustion that can lead to build-up of carbon and other deposits within the engine. From a thermodynamics standpoint, an automobile engine is actually operating most efficiently at the highest temperature possible within its design parameters.

Besides, how can it never be too cool a temperature for an engine to run at? Is it ok if it never gets, say, above room temperature? Of course not. So we've established that there is a lower boundary for operating temperature. Now the question is, exactly how low is it.

How would you recognize an engine running too cool if it was right in front of you? There are no outward symptoms of it like there are if it is overheating. The consequences of running too cool are subtle and build up over time. They're not all-of-a-sudden problems like a blown head gasket or burst radiator hose leaving you stranded on the side of the road.

rustyroger

An overcooled engine can suddenly and seemingly for no reason suffer pistons partially seizing.
I have seen this occur mostly in re-bored engines run without thermostats.


Modern engines are machined to much closer tolerances than back in the bad old days. This is one reason modern engines last much longer than older ones.
However when an engine warms up the bores expand slightly, so do the pistons. The pistons will rapidly warm up to normal operating temperature and expand accordingly, the bores which are kept too cool will not expand to normal temperature dimensions, occasionally, particularly if the engine is given some beans, partial seizures can occur.
This is a more frequent phenomenon with diesels than gasoline engines, the pistons are much more substantial in a diesel.
Some would argue; "Well why doesn't a partially warmed up engine do this?".
My answer is its not that the piston sides become too large for the bore, rather the oil film cannot be sustained, and galling occurs, the lack of oil also prevents the oil from doing its secondary but very important job of heat removal.
Racing engines often run a restrictor rather than a thermostat, but they are normally warmed up before a race, and would be running with the throttle wide open most of the time, effectively running like a thermostat controlled engine after warm up.


Another consequence of overcooling is the engine oil not getting hot enough for moisture to evaporate from it, not to mention an ineffective heater in the winter.


Roger.

CutlassDad

I am recently retired from 25+ years in the heavy duty diesel industry, 20 years of which was in cooling performance and radiator selection.

I have spent more than a little time thinking of a way to explain the full blown radiator selection process, but always run headlong into the what do we know about the engine heat input, coolant flow, cooling airflow in CFM, radiator performance and many more variables questions.

With very little or no accurate information on any of those variables, trying to determine the fan, radiator, or water pump performance required to maintain a set of temperatures is difficult to the point of being impossible.

jaunty75

Thanks for your very interesting post, and this point in particular is one that I hadn't thought of. This is a problem for cars that are driven mostly short distances where the engine can often never fully warm up, and water accumulates in the crankcase, sometimes to a significant degree. I remember hearing them talk about this once on CarTalk some years ago. The engine at least has to reach the boiling point of water, 212 F, if any water in there is to be boiled off. It's also another reason why frequent oil changes are a good idea.

jaunty75

This is pretty much the point I was trying to make in my first post in this thread, but you've done a better job.

You buy, say, a new 1968 Olds with a 455 engine, and it comes from the factory with a certain size water pump, certain size radiator in terms of number of rows and coolant capacity, a certain size fan, and a thermostat of a certain rating. This was all designed as a unit, and people come along and say "oh I think my engine is running too hot so I'm going to put in a different thermostat or a larger radiator" without any consideration as to how this affects the system as a whole.

Most cars back then didn't even have a temperature gauge, just an idiot light, so you didn't know what the engine temperature was at any given moment, anyway, and you never worried about it. You just drove the car.

But then they install a gauge, see what the temperature really is and how it rises a bit while they're idling in traffic or at a stoplight, and they start panicking and wanting to make changes.

Don't fix what ain't broken.

oldcutlass

Engines can and will run too cool if setup improperly, this is caused by people who try to get the summer time temps down. Then winter comes around, yes some go into hibernation, others are still driven. Another side note is in the winter on an over cooled engine the automatic trans will not reach the proper operating temp either. Another side effect is the lack of heat inside the car and so on.

Also note that the red idiot light does not come on until 230+ degrees.

tkheld

Jaunty75 - you have captured the essence of my original question. If the guy the 1968 Olds with the 455 has all the same original equipment, but just wants to replace the radiator, there is a dizzying array of radiator choices - ranging from $100 to $1000.

Since I have yet to discover some uniform method to determine radiator cooling capacity, I was hoping someone had some guidance on how to select a replacement radiator.

I do appreciate all the feedback. It still burns when I put my tongue on it

Fun71

What I did was find out what the original radiator was: length x height, number of rows of tubes, number of tubes per row, size of tubes, and number of cooling fins per inch.

Then I looked for a replacement radiator with the same overall size (length x height), but with some combination of more rows of tubes, more cooling fins per inch, or larger diameter tubes. Getting all three would be a good thing.

What happens sometimes with aftermarket radiators is there are FEWER of one or more of those items compared to the opriginal radiator, which translates to less cooling capability instead of more.

68442Convertible

I installed a set of gauges, figured out that I was running hotter then normal most of the time. I took my 68 radiator to a decent shop. They tested it and determined it needed a new core. So I had it recorded. I also replaced pretty much everything in the cooling system. Works much better now.

brown7373

The idiot light for 1972 Olds engines were designed to come on at 248 degrees (258 for Toronado), and I would think your year is similar. 190 is 58 degrees below what Olds engineers decided was hot. What jaunty said is so true about watching the gauge temp rise a bit and panicking. I read an article recently about why modern gauges seem to show constant temperature with very little variation. The article said that modern cars have gauges calibrated to average temperatures, or smooth them out, because customers thought they had a problem when temperatures fluctuated a little bit. When I had cars with idiot lights, I rarely thought about temperature. But I find with gauges, I am constantly checking the gauge.

tkheld

Found the info below posted on another site. Answers some of my original questions. Thought it would be good info to pass on.


"PutA Cap On Your Radiator Problems!!
What makes the better radiator;
Aluminum or Copper?

I get asked this question so often that I feel like a broken record telling thepros & cons over and over. I am not a scientist, chemist or engineer butbased on my 28 years in the radiator business here is my opinion on which isbetter; copper or aluminum radiators.

There is much debate over whether a copper or an aluminum radiator will coolbetter. There are pros and cons to each material. It has been scientificallyproven that copper actually transfers heat better than aluminum. It is easierto repair in most cases than aluminum and until the last couple of years wasmuch less expensive. The drawbacks to a copper radiator are the weightdifference (aluminum is much lighter) and the solder joints that hold ittogether. The solder that secures the tubes to the fins does not transfer heatas quickly as copper and slows down the heat transfer. The presence of solderwhere the tubes are soldered into the headers is also the main cause of what isknown as “solder bloom”. I am sure all of you have looked inside a radiator atsome time and observed the white residue growing around the tubes. This growthis the result of chemical reactions from different metals (brass tubes, copperheader, lead/tin solder) and lime and other chemicals in the water/antifreezemixture. In the 1990’s some manufacturers started using a process called“Copubraze” which eliminated the solder between the tubes and the headers. Thetubes were brazed instead of soldered which prevented the solder bloom problemand also created a better made core. This process was more costly however andmost manufacturers were favoring aluminum anyway due to the weight savings.Copper core manufacturers also started using smaller and thinner tubes to breakthe coolant down into smaller amounts to further improve cooling. Smaller tubesclogged up much easier especially when the vehicles owner did not adhere to recommendedcooling system flushing intervals. They also used thinner material to cutweight and improve heat transfer but the longevity suffered.

Aluminum radiators are welded or “aluminum brazed” and the finished piece is100% aluminum. This eliminates the dissimilar metals and solder bloom problemsthat affect copper radiators. Aluminum radiators can also use wider tubes thatcreate more surface contact area from the tubes to the fins and helps dissipatethe heat quicker. Most aluminum radiators use 1” wide tubes and somemanufacturers like Griffin offer 1.25” and 1.5” tubes as well. Traditionalcopper radiators usually use ½” tubes so a 4 row copper radiator has slightlyless fin contact area than a 2 row aluminum core with 1” tubes when you takeinto account the loss of contact area at the curved ends of the tubes. Most OEMcopper radiators were built with the tubes on 9/16” centers from each other.All aluminum cores are built with the tubes on 7/16” or 3/8” centers creating adenser and more efficient core than a standard copper core. I generally tellcustomers that a high efficiency (tubes on 7/16” or closer centers) copper fourrow will cool the same as an aluminum core with two rows of 1” tubes. If morecooling is required from the radiator than either of these designs willprovide, than an aluminum core with two rows of 1.25” is the thickestrecommended for a street application. Any thicker than that and you may havetrouble pulling air through the core at low speeds or when at a light.

Aluminum offers the advantage of about 30% to 40% less weight. To a racer thisis a huge advantage over copper. Aluminum can also be polished out to a mirrorlike finish for those concerned with show appearance. Neither has an advantagewhen it comes to corrosion. Left unprotected, a copper radiator core will turngreen and deteriorate rapidly especially in a damp environment. That is whycopper radiators have always been painted, usually black. Aluminum will oxidizeif not protected from the elements.

If your radiator needs to be replaced and you want to retain as muchoriginality as possible then recoring your original copper radiator may be thebest choice for you. A copper radiator core can be made more efficient bychanging the tube spacing and fin count. As I stated earlier the radiators thatwere made from the 1950’s to the 1970’s generally used ½” wide tubes placed on9/16” centers from each other. If you counted the fins you might get as few as6 or 8 fins per inch (FPI). If the tubes are placed closer together and thefins are packed in tighter a denser core is created that throws off much moreheat. A high efficiency core can have tubes on 7/16”, 3/8” or even 5/16”centers and fin counts increased to 12 to 14 FPI. That may not seem like a bigdeal but the surface area is greatly increased. As an example; a 26” wideradiator core with tubes on 9/16” centers has about 45 tubes from side to side.A high efficiency core of the same width has 57 tubes from side to side.Combined with all the additional fins between the tubes this providesapproximately 25% to 30% better cooling than the OEM radiator had. A three rowhigh efficiency core will cool about the same as a regular four row withouttaking away another 5/8” of fan clearance. Going to a thicker core will cool betterbut there is one big thing to remember. As the air passes through each row oftubes it is picking up heat along the way. The air cools off each following rowof tubes a little less than the previous rows. A four row core is of coursebetter than a two row core but increasing a cores thickness does notnecessarily mean it will continue to get more efficient as it gets thicker. AsI said earlier a core that is too thick will also impede the airflow at lowspeeds.

So which is better, aluminum or copper? My opinion is neither. Each one hasadvantages over the other in different areas. The decision over which to use inyour particular case comes down to what is more important to you. Weight,appearance, originality and cost all need to be considered before you make yourdecision. From my own experience on my own vehicles I have found that aproperly built high efficiency copper radiator will cool the same as a wellmade aluminum radiator. Like I said at the beginning, I am not a scientist oran engineer but this is my opinion and I’m stickin’ to it.

Cap-A-Radiator
566 Fulton Street
Farmingdale, NY 11735
(516) 293-9026
Hours of Operation:
Mon-Fri 8am-5pm
Alternate Saturdays 8am-1pm"

jaunty75

I like the article, but comments like this drive me crazy because it implies that some major experiment was performed just last week proving the assertion. All you have to do is go to a handbook and look up the thermal conductivities of the metals in question.

http://en.wikipedia.org/wiki/List_of...conductivities


In units of Watts per meter per Kelvin, copper's thermal conductivity is 350 to 400 depending on the source, while aluminum's is about half this at 200 to 250. But relative to most other metals, these two are quite high. Actually, if you really wanted high heat transfer in your radiator, you wouldn't make it out of copper or aluminum but rather silver as silver's thermal conductivity is a little higher than copper's and is the highest of any metal. But silver has other drawbacks that make it unsuitable.

Thermal conductivity correlates with electrical conductivity (the movement of electrons, for the most part, is the mechanism in both cases), and this is why copper is the metal of choice for wiring while aluminum was actually used in residential house wiring for a while. I don't know if it still is. There were problems in using aluminum involving metal mismatch when connecting to fixtures, so if aluminum wiring is used, special connectors must be used.

Smitty275

For what is readily available I'd have sat that the aluminum radiator with plastic tanks is the best. Cost, function, durability, they are just hard to beat.
As for capacity needed that's a hard one to determine. Do you worry about being able to cool at average operating conditions with the ability to absorb short bursts of maximum heat out put or do you just worry about being able to cool at max out put? Personally I'd aim to be able to cool properly at any level and control with a thermostat for when you don't need the full capacity.

oldcutlass

jaunty,

"The main problem with aluminum wiring is a phenomenon known as
"cold creep". When aluminum wiring warms up, it expands. When
it cools down, it contracts. Unlike copper, when aluminum goes
through a number of warm/cool cycles it loses a bit of tightness each
time. To make the problem worse, aluminum oxidises, or corrodes
when in contact with certain types of metal, so the resistance
of the connection goes up. Which causes it to heat up and corrode/
oxidize still more. Eventually the wire may start getting very hot,
melt the insulation or fixture it's attached to, and possibly even
cause a fire."