Need radiator advice, please: 69 SWB Stepper

[fishyalien]

Hello evreyone! I have gleened a bunch of great information from this forum and all its members over the past 2 years that I have owned my truck.I need some advice and this time when I searched for the answer but couldn't find a recent answer.

While putting in a new engine and rebuilding the transmission, i decided to take the radiator to a local shop to have it tanked and checked. Or course, like everything else on the truck, it is in need or work - namely the core is badly plugged. They said they can put a new core in it (it isnt a 4-core) and re-use the tanks. The only real value of that is original look because they want just over $300.

I find O'Reillys and Autozone have aluminum/plastic units for $184. All aluminum seem to go for $325+ Cost is weighing heavy because I have already put a lot into it.

What are you doing for a replacement radiator?

[LockDoc]

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I would try to find a good used original close enough that I could go pick it up. I don't think that would be too hard in your location. I'm pretty sure Art's Classic Truck Parts In Indianola, IA would have one. You could do a short road trip, meet a great guy, and check out his trucks....

Art -515 321-0959

He's a real truck guy, not just a store front. Tell him Leon sent you.

LockDoc

[fishyalien]

Great, thanks for the advise and referral. I will give him a call and see what he has. Always good to chat with another truck guy too!

[71tahoe]

There is one on ebay with free shipping. $214.80:

http://www.ebay.com/itm/APDTY-100-Al...c4b244&vxp=mtr

searched "67-72 chevy truck radiator"

[67 cst swb]

Having worked in a radiator shop for awhile (see my history of posts started by me) I just want to mention this...
a re-cored original radiator will definitely be the "best quality" option you have. The quality of the metal in the tanks... plus the quality of the materials used when manufacturers build replacement cores is far superior to any aftermarket product out there. Plus it stays 100% original in appearance. That's not to say that the replacement radiators are crap... It's just to say that replacement radiators are not the same quality of materials as what a recore with original tanks would be.
I see that in the near future it will be difficult to find a replacement copper/brass radiator for our trucks as all the suppliers are going to plastic/aluminum (like the newer vehicles have) they are an adequate replacement, but they look out of place in out vehicles.
And as far as the all aluminum performance radiators... I have not seen one (in person) that fits perfectly into the saddles. But, I have not seen them all of coarse.

Here is MY order of preference for using replacement radiators.
1. repaired original radiator (repaired by a radiator shop)
2. re-cored original using original tanks
3. replacement copper/brass radiator by a reputable company
then..
4. All aluminum performance radiator (first choice if in a performance application or truck with billet, chrome & polished everywhere
then a distant...
5. replacement plastic/aluminum (this is what all companies are going to as plastic & aluminum is much cheaper to acquire then copper & brass.

And... NEVER use that pour in the radiator stop leaks (unless its an emergency)
use of this stuff will surely end the possibility of your copper/brass radiator being "repairable" as it becomes cement in the tubes and it never comes out, so you are looking at a re-core at that point.
keep in mind, this is just my opinion.

['68 Short Step]

http://www.oreillyauto.com/site/c/de...yword=radiator

I got this 4 row from oreilly's. looks similar to the original and works great.

[Hugh Mongus]

I bought a 3 row from Ebay yesterday. It's all aluminum and cost $172 free shipping. I can post up results once i get it installed.

[Z10]

I purchased this 2 core radiator and have it installed in my 72 cooling a ZZ4. Cools like a champ and the tanks are similar to the factory tanks. Also, you'll get better cooling with a 2 core.

http://www.speedcooling.com/1967-197...r/prod_38.html

Check on my build thread for more photos.

[litew8]

Originally Posted by LockDoc

-
I would try to find a good used original close enough that I could go pick it up. I don't think that would be too hard in your location. I'm pretty sure Art's Classic Truck Parts In Indianola, IA would have one. You could do a short road trip, meet a great guy, and check out his trucks....

Art -515 321-0959

He's a real truck guy, not just a store front. Tell him Leon sent you.

LockDoc

He's got some nice ones, for sure.

[Z10]

This might help also.

One thing to remember is that the 3rd and 4th rows are not as efficient because you are pushing heated air from the first 2 rows.

I found this thread to be helpful, it's lengthy, but well written.

"There is considerable misinformation regarding what makes a radiator transfer heat (so take what you read with a grain of salt).

Ill try to make a short radiator and heat transfer for dummies post

Heat is transferred from the coolant to the radiator mass, and from the radiator mass to the airflow. The temperature difference at each transfer junction (coolant to metal, and metal to air) drives the quantity of heat transferred.

Aluminum weighs less, and the lower mass allows it to transfer heat more quickly than brass. The steady state heat transfer between the two materials (aluminum and brass) is very similar, but aluminum reacts quicker to a change in the temperature difference of the coolant fluid (like when you are on the throttle) because the heat transfer takes less time heating up the mass of the radiator itself before establishing the temperature difference between the radiator and the airflow. The fact the aluminum experiences an elevated surface temperature quicker allows it to reject the heat into the airflow quicker.

When the radiator is underdesigned (to reduce weight or fit a poor location) this rapid thermal response provided by aluminum can make a difference in overheating (or not) after a brief period of WFO travel (like in racing). When the load is steady state (a fixed industrial engine or a long crawl up a grade towing), the response time benefit is insignificant because while the brass takes longer to respond, having the proper area for heat transfer is more important (both radiators eventually reach the same steady state temperatures and the same heat transfer rate).

Sizing the face area of a radiator core to have one square inch for every cubic inch of displacement has been around for a long time (400 ci. engine matched to a 20"x20" radiator). This rule of thumb does not work everywhere (dry deserts need more face area) so some add 10% or more extra face area.

Core thickness is an airflow restriction on the air side (bad for heat transfer), and more tubes (one tube per core) increases surface area (good for heat transfer) on the coolant side. Multicore radiators are great for getting the radiator metal hot, but not always great for getting that extra heat into the air, and the hot air away from the radiator.

The coolant to metal transfer is fairly efficient, because both materials (coolant and metal) have significant mass to store the heat being transferred. The heat transfer junction, the required wetted area of the tubes inside the radiator core, can be calculated with fairly good accuracy. The surface area can be accomplished with more small oval tubes (1/2" and 5/8" typical of brass radiators) or with fewer larger tubes (typical aluminum 1" and 1 1/4" tubes). Go with the most tubes (cores) for the greater surface area, if the fan drive can handle the airflow restriction.

The aluminum radiator core manufacturers already take any credit for the more rapid thermal response of aluminum when calculating the tube surface area, they use the minimum surface area they can design, so further reducing the face area of the core (to try and squeeze even more efficiency from the aluminum construction) is risky unless the design can be tested and adjusted (if the budget allows doitagain engineering). I advise against reducing the face area of the core, and any thinking that the material choice allows a discount factor to the heat transfer potential, unless you are racing to shave weight and the load is transient.

The coolant side of each core tube sees the same temperature coolant flow and the same rate of heat transfer from the coolant to the radiator core metal. The result is the radiator metal is almost always the same temperature with minimal gradient front to back. The coolant to metal heat transfer is the same for each core (what heats the radiator metal is the same), and the coolant temperature leaving each core (to be delivered to the engine) is nearly the same, but the air side of the radiator is not so simple.

The discount factor for heat transfer on subsequent cores is only on the airflow side. The face cores experience unheated air, and subsequent cores experience air at a higher temperature.

The best heat transfer occurs where the greatest difference between the air temperature and the radiator metal is found, the face or entering side of the radiator. If you want the best heat transfer, increasing the face area of the radiator metal that sees cool air will gain you the most impact for your effort (a larger radiator face will beat more cores nearly every time).

The construction of the radiator fin design is important to the increase in temperature through subsequent cores in series, and is related to a "bypass factor" that models how much air bypasses heat transfer from direct contact to the surface area of the fins. The mass of air that can squeeze between (bypass) the fins without picking up heat mixes with the mass of heated air that does make contact, and the result raises the air temperature of the downstream cores.

In reality, without getting into math or fin designs, the elevation of air temperature between cores is less than 15%. If the airflow temperature is raised from 70dF to 170dF through a four core radiator, a 100 degree increase, 45 degrees (~45%) of the temperature rise (and heat transfer) is in the air to metal contact in the first core, and a lower percent from subsequent cores (something like ~30%/17%/8%).

The aluminum radiator guy's are right that two cores are more efficient (nearly 80% of the cooling is from the two front cores), but if the total surface area of the coolant to metal, and metal to air, contact is less ... the net result is not so great of a design (just like ricers 100 ci 4-banger @ 3 hp/ci is good, but nothing like a 302 @ 1 hp/ci: there is no substitute for more surface area in a radiator unless you want to spend a lot).

The actual area of the core face that experiences the high air to metal temperature difference is more important than the calculated face area. People tend to forget that the radiator face is not working to transfer heat, unless it's moving air.

What makes air flow through a radiator core (through a restriction)? Pressure drop (static pressure) or the momentum of the air mass (velocity pressure) through the core establishes the airflow, and the resulting heat transfer.

Most people with a cooling problem try to increase the mass of air blowing through the radiator by increasing the velocity pressure acting on the core. They add a round fan (usually electric) in front of the radiator (a pusher fan).

When an unshrouded fan is used, a puller with no shroud or a pusher, the core area experiencing the airflow (and temperature difference) is limited to only that is the direct path of the high velocity air. A 20x20 (400 sq.in.) radiator face with a 16" diameter fan blade, without a shroud, is little better at heat transfer than a radiator with a 16" round (201 sq.in.) face area.

Adding a 16" pusher in front of this radiator, with the unshrouded 16" puller, gains almost nothing in air side heat transfer effect.

How do you get the entire entering face of the radiator to work transfering heat? You try to get airflow across the entire face of the radiator core.

Try many small fans (fit lots of round high velocity airstreams in a square area)? It can work, but it's looks complicated (and is probably expensive).

It's easier to make a static pressure difference across the radiator core work to move air through the entire face of the radiator, by using a puller fan and fitting a shroud on the suction side of the core. You only need one fan, and it can motivate airflow across the entire face area of the radiator core, just by adding a shroud to contain an area of negative pressure on the leaving air side of the core.

The problem with using static pressure to draw airflow through a radiator is that it takes a significant increase in power to generate pressure (research fan laws). Using a multicore radiator core that is thick and restrictive on the air side requires that it be matched with a fan and shroud that can generate a static pressure difference great enough to overcome the restriction.

Replacing a two core with a more airflow restrictive four core can sometimes work against you if the fan clutch is weak, or it is combined with a swap to an electric fan.

Most electric fans cannot develop significant airflow at higher static pressures, because the power draw must be limited to protect the wiring. Compare an electric fan to a high flow (and pressure) mechanical fan. The blades of the electric are narrow, and the blade pitch is shallow (compared to the mechanical fan), both design aspects limit the potential of an over-amp condition. Yes, electric fans are great to gain power on the end of the crankshaft, because to generate a significant negative pressure behind the radiator sometimes takes three to five horsepower (the gains we read in the electric fan advertisements). Use electric fans when you can, when the radiator is overdesigned for the power and transient heat transfer required, and use a shroud. Just do not expect a 1/4 hp electric to pull the same airflow and pressure drop of a fan drawing 3 hp off the front of the engine.

I read that fans have little effect to gain airflow at speed ("airflow is going through the radiator on the highway because you are going faster, so adding a fan or shroud to cool the engine on the highway is not going to solve the problem.") We read it all the time. It's BS.

What is difficult to understand is that most vehicles generate a high pressure area under the chassis at speed (the air above and to the sides of the vehicle is high velocity/low pressure, but underneath it's low velocity and high pressure). Yes, the pressure in front of the radiator can be higher (conversion of the velocity pressure to static pressure) but the pressure behind the radiator can increase with speed as well. Betting that the converted high velocity air in front of the vehicle radiator can overcome the pressure under the vehicle (the pressure on the leaving side of most unaided radiator cores), to motivate airflow, is almost like betting that you can piss up the inside of the airhose of your compressor with 20 psi streaming out the end.

You still need a fan and shroud to eliminate most radiator airflow problems at highway speeds, because you still need to establish a pressure drop across the radiator core (and sometimes it's more difficult at 60 mph, than when parked at the curb).

Crossflow vs. downflow design is not as important as where the radiator cap pressure relief is located. The cap should be on the low pressure side of the water pump, something that is easier to package and service with a crossflow core.

I hope this helps (I have had enough internet tech for the week)?

In summary: if the budget demands a choice between a high dollar aluminum radiator, or a brass radiator and a well fitting shroud, get the system with the shroud (and use a mechanical fan drive with a fan blade that has some pitch angle to the blades, and a clutch to save power when it's not needed).

Happy Trails!

[TheSeeker]

Wow, A lot of interesting info there! I have a stock 6 cylinder radiator in my truck now, If I order that aluminum one you posted and add AC do you think it would cool effciently in 100+ degree heat in the AZ summer? Thanks!

Also, if I am correct, I wont need the larger core hold downs if I used that one?

[litew8]

Most likely, yes it will. I have an aluminum rad and I might actually have an issue of running too cool. Something to think about.

[fishyalien]

Wow, You all never cease to amaze me with the knowledge and experience!

Based upon this, I am going to call Art for a good used one today, and if that doesn't pan out I am thinking this 3 row aluminum would be a good fit since I have a 3 row no:. http://www.ebay.com/itm/400628716371...%3AMEBIDX%3AIT

Looks similar to 71Tahoe, Hugh Mongus, and Z10 recommendations.

I will be running the factory shroud with the Cherokee electric fan (from another thread here). I plan to use a pusher fan when the AC is on. The tech article Z10 provided affirms that fan approach if I read it correctly. That is an excellent write-up by the way.

Thanks, I will let you know what I find.

[Lee H]

You can get an all copper brass, 4 row, direct fit, at your local auto house for 200-250. Returns are easy, warranted forever, and you support your local community.

[67 cst swb]

Originally Posted by Lee H

You can get an all copper brass, 4 row, direct fit, at your local auto house for 200-250. Returns are easy, warranted forever, and you support your local community.

I agree...

[cdowns]

me too/ buy local

[SparkyRnD]

If you decide you want an aluminum replacement, we are a supporting vendor and make custom hand-made radiators right here in the USA, and we offer a forum discount

http://67-72chevytrucks.com/vboard/s...d.php?t=590670

[jeffro308]

Originally Posted by 67 cst swb

Having worked in a radiator shop for awhile (see my history of posts started by me) I just want to mention this...
a re-cored original radiator will definitely be the "best quality" option you have. The quality of the metal in the tanks... plus the quality of the materials used when manufacturers build replacement cores is far superior to any aftermarket product out there. Plus it stays 100% original in appearance. That's not to say that the replacement radiators are crap... It's just to say that replacement radiators are not the same quality of materials as what a recore with original tanks would be.
I see that in the near future it will be difficult to find a replacement copper/brass radiator for our trucks as all the suppliers are going to plastic/aluminum (like the newer vehicles have) they are an adequate replacement, but they look out of place in out vehicles.
And as far as the all aluminum performance radiators... I have not seen one (in person) that fits perfectly into the saddles. But, I have not seen them all of coarse.

Here is MY order of preference for using replacement radiators.
1. repaired original radiator (repaired by a radiator shop)
2. re-cored original using original tanks
3. replacement copper/brass radiator by a reputable company
then..
4. All aluminum performance radiator (first choice if in a performance application or truck with billet, chrome & polished everywhere
then a distant...
5. replacement plastic/aluminum (this is what all companies are going to as plastic & aluminum is much cheaper to acquire then copper & brass.

And... NEVER use that pour in the radiator stop leaks (unless its an emergency)
use of this stuff will surely end the possibility of your copper/brass radiator being "repairable" as it becomes cement in the tubes and it never comes out, so you are looking at a re-core at that point.
keep in mind, this is just my opinion.

What he said^^^^ Those RnD radiators look good though. The PO of my 69 panel used an improperly-fitting aftermarket.