Some radiator questions

[48builder]

I'm making so much progress, that I'm thinking about firing this thing up soon. Before I do, I need to get a radiator in it. Since I have a subframe, I'm not really limited to the stock size. I can go up to about 26" wide and similar height.

I have found a few that may work, including late-model DodgeVan and Durango.

Should I limit my search to copper or aluminum? I don't really care. I guess aluminum transfers heat better, and saves a little weight.  The Durango is aluminum, while the van is copper. Both are 2-row, and about the same size.  The Durango is more expensive, but still a heck of a lot cheaper than the Walker I have in my '39.

I welcome all comments and other ideas.

[enjenjo]

Copper actually transfers heat better, the reason all the late models have gone to aluminum, weight, they are much lighter.

I have used the Dodge Van radiators on several cars, seem to have no trouble cooling.

[Bruce Dorsi]

Hi, Walt!

I would choose the copper radiator over the aluminum version.  

IMHO, the copper will outlast the aluminum, especially on a vehicle that may not see alot of use.  

The aluminum radiators seem to be more prone to corrosion.

...my $.02

[HOTRODSRJ]

I have to take exception to the latter posts with all due respect.  While there is nothing wrong with copper/brass/solder radiators,  aluminum radiators are constructed from much larger tube sections meaning that they increase flow, have higher BTU transfer and are far more efficient than copper/brass/solder. Almost 50% comparing area to area.  Most 1" dual tubed aluminum radiators will easily out cool a 5 row c/b/s conventional styles.

The reason most OEM manufacturers use them is that they are more efficient, which means they can use a smaller area profile, which follows lower hoodline designs.  Yes, weight is an issue too, but mainly they are selected for their efficiency.  Also, contrary to popular opinion, they are far more rigid, LESS prone to leaking and will take far more pressure than conventional styles due to thicker walls and welded construction.

While copper conducts heat better, the overall surface conduction of the larger aluminum tubes far outstrip the coppers shear performance. Also, solder is a terrible conductor of heat and copper radiators are floppy compared to aluminum ones.  

There are some generic aluminum radiators around from Summit that are very good and cheap.  Also, check out www.streetrodstuff.com/Products/157 for the custom made jobbies!

Stay away however from multi-pass radiator designs. These require much more pressure to move the flow.

[moondisc]

Stay away however from multi-pass radiator designs. These require much more pressure to move the flow.

I had the stock radiator re-cored in the 41 with a multi pass core.
It'll idle around the fairgrounds all day long in 95 degree heat, and barely hit 190.
It has a 7# cap on it.

[HOTRODSRJ]

Stay away however from multi-pass radiator designs. These require much more pressure to move the flow.

I had the stock radiator re-cored in the 41 with a multi pass core.
It'll idle around the fairgrounds all day long in 95 degree heat, and barely hit 190.
It has a 7# cap on it.

I believe ya!  Nothing necessarily wrong with multi-passes, but the most efficient design for street applications and especially slow cruising and variable RPMs would be large-tubed, all aluminum, single-core designed cores.  This is because double pass radiators require 8x more pressure to flow the same volume of coolant through them as compared to a single pass radiator....and triple pass radiators require 12x more pressure to maintain the same volume.  Since automotive water pumps are a centrifugal design and not positive displacement in a double pass radiator the pressure is doubled and flow is reduced by approximately 33%. OEM or  modern radiator designs, using wide cross sections tubes, seldom benefit from multiple pass configurations due to the decrease in flow caused by multiple passe design.  With decrease in flow so goes the reduction in turbulence as well.    These could easily offset any benefits of a high-flow water pump you may have added.

Simply put, the single-pass designs are superior for street use.  This does not mean that the multi-pass will not suffice in certain applications.  I threw the warning in my previous post because alot of the "universal" and/or "racing" radiators are multi-pass designs.

On the other hand, applications where the RPMs of the motor/water pump are constant and high (such as racing and certain hauling situations), multi-passes are as good or better in some cases depending on use.

[moondisc]

Well Steve, you're the engine-er and I can't even spell it, but it seems to me the longer the coolant stays in the radiator the more heat it's going to transfer.
Take the thermostats out of a flathead, it flows more volume. And overheats.
BTW my 41 has a 7 blade Volare steel fan, no shroud, and a stock 350 Olds.
My bud has the same combo in his Olds with with a shroud and the biggest alium rad he could get in it, and it overheats after about 10 min at an idle.
Like I said, I ain't no engine-er, but I know what works!  

[41woodie]

Ok, when you talk about multi-pass aluminum radiators are you talking about the style that Griffin makes?  I'm running a stock radiator w/o shroud on my woodie and am in the process of replacing it with aftermarket, want to get all of the input possible before $$$ walker vs. griffin vs. US Radiator etc.  I will definitly be using a cooling components electric fan and shroud combo.

[moondisc]

I had a US Radiator in my 37, and I wasn't at all happy with it.
It sprung leaks around the filler neck, top hose connection and top tank.

[41woodie]

I had a US Radiator in my 37, and I wasn't at all happy with it.
It sprung leaks around the filler neck, top hose connection and top tank.

What did you replace it with? or did you repair it? MH

[moondisc]

What did you replace it with? or did you repair it? MH

I just kept fixing it. Over and over again.
Sold the car after that.
Check the link Steve posted above for PRC radiators.
Everyone that's used them said they're great, and their prices look good too.

[Bruce Dorsi]

... it seems to me the longer the coolant stays in the radiator the more heat it's going to transfer.

------------------------------
I've heard this said many times over the years, but I have to ask, "What happens to the coolant in the engine while it is staying in the radiator longer?"

It seems to me the longer the coolant stays in the radiator, the coolant in the engine is getting hotter than if it were flowing faster.

Thinking about it another way, if the coolant picks up 30 degrees in the engine, the radiator only has to "lose" 30 degrees to the ambient air.   .....If the coolant gains 80 degrees in the engine, the radiator must now be capable of losing 80 degrees to the ambient air.

Many OEM GM set-ups overdrive the water pump by as much as 28% of engine rpm to speed up the waterpump.  ....If lower flow rates were the answer, I doubt the factory would do that.
 
I realize there are other factors which affect heat transfer, and this may be an over-simplification of the conditions.  ...We may also be "splitting hairs," with little difference in results.

What IS important, is having a radiator capable of losing the heat produced in the engine.  ...If the engine produces more heat than the radiator is capable of losing to the ambient air, then overheating WILL result.

As has been discussed many times, ignition timing, fuel mixtures, and airflow through the radiator have a great influence on operating temps, ...probably as much as (or more than) radiator type or material.

Also, size does matter!  

[48builder]

What do I do. So HOTRODSRJ, by single tube do you mean 1 row? I ask beacuse one fo the radiators I am considering is from a 2000 Durango with V8, and it says it has 2 rows. Would I be better off with a 1998 version with 1 row? Both of them have larger surface area than the one from my '95 Z28 donor car.

And speaking of my Z28, the LT1 motor has an electric water pump, so I am assuming I would want to stick with an aluminum radiator because it may not be able to produce enough pressure for a copper unit?

[HOTRODSRJ]

Don't confuse "rows" or "tubes" with "passes".  Large tubed, dual row aluminum radiators are the conventional and most efficient design.

Also, most of the Griffins that I have seen are single-pass design.  I don't think they make multi-passes.  So, Griffin has one of the best designs on the market, albeit expensive.  

Also, on another front .....I have fought this "myth" for years in many differing forums.  Simply put, the more flow the higher the efficiency of the cooling system.  This is why high flow water pumps where invented and "overdrive" pulley systems.

Also, the explanation of the coolant sitting in the radiator while slowing the flow is exactly right on.  The coolant in the engine is sitting trying to absorb heat as well.  This is a closed-loop system.  And as the coolant rises towards its corrected vapor point (boiling point at pressure XX) it loses it's ability to absorb heat.  So, for example, it takes more volume of 185 degree water to remove the exacting same amount of BTUs than 165 degree water.

One of the most interesting "layman's" explanation of how "flow" effects cooling came from a Doctor that I designed a cooling system for his muscle car.   When he inquired about the "science of flow" thing I gave the thermodynamics explanation of what happens.  He says, "I should have know this....this is the very same way the human cooling system works?"  Going on he states, "When the body needs to be cooled the lungs and skin both act like a radiator exchanging heat to air.  The blood vessels open up to increase the flow and moreover the heart is like the water pump in that it will increase to move the blood (which is the coolant) at higher flow rates.  The increase in flow is what turns up the efficiency of the system to cool as fast as you can.  Your breathing frequency increases as well to also increase heat exchange at the lungs.  Conversely, when you are in a cold atmosphere and the body is trying to keep warm it shuts down the blood flow by lowering heart rate and dialating blood vessels (which also lowers flow) and slows breathing."  So, that's one of the best analogies that I have heard.  

The other issue is increasing flow increases turbulence. But this is not always the case.  I have heard about the flatheads and taking the thermostats out purportedly increasing the flow and having overheating problems.  What happens is that the cause and effect and therefore the deduction is faulty.  What happens is that by taking the thermostats out the flow stream becomes extremely laminar and non-mixing.  The lack of the usual turbulence caused by the exit of the thermostat makes the efficiency of the system lower.  Simply putting large hole reducers in place of the thermostat reintroduces turbulence and should cool better.

[Leon]

Ron Davis in Glendale, AZ makes a nice radiator.  I'm very pleased with the construction of mine.  Price was decent, too.