3 or 4 core radiator

[Robert Bergstrom]

What was the stock radiator for a 72 half ton with a 350 and A/C? I have a used 3 core and need to know if it will handle the cooling for my 350/700R with A/C. Do I need a 4 core?

[litew8]

doubt it

[Stocker]

Not positive but I think the stock radiator is a 2-row. I believe that's what my K20 came with. I replaced it years ago because it was rotted. I bought a 4-row but a 3-row should work just fine. This assumes the radiator is good as well as all other components of the cooling system, including water pump, t-stat, clutch fan and shroud.

[DeadheadNM]

Stock in an A/C truck is 4 row...

[flashed]

My truck (72 shortbed 350/350 )everything new ,just frame off restored and with Vintage Air will run HOT with the air on and it has a 3 row radiator ,just ordered a 4 row aluminum radiator and a clutch fan to hopefully cure the running hot issue .

[Robert Bergstrom]

Thanks, I will Craig's list the 3 core. It is a good used radiator. Did not want to spend the $$$ for a nice aluminum but will. What is a good brand? Anyone.

[flashed]

I dont know what brand mine will be I just ordered it from Southern Kentucky Classics but it is currently on backorder .

[litew8]

Here's a decent discussion http://www.hotrodders.com

[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!

[Stocker]

Originally Posted by DeadheadNM

Stock in an A/C truck is 4 row...

It wasn't in my K20 with factory A/C. Might have been a 3-row but definitely was not a 4-row. Moot point anyway for the OP because he's gonna upgrade.

[litew8]

good graphic

Originally Posted by 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.

...

[litew8]

Originally Posted by Stocker

It wasn't in my K20 with factory A/C. Might have been a 3-row but definitely was not a 4-row. Moot point anyway for the OP because he's gonna upgrade.

2 row brass/copper are real skinny I think

[litew8]

Originally Posted by Robert Bergstrom

What is a good brand? Anyone.

I haven't looked to compare, but I got good results with this vendor. The price was less than Summit's. I don't think Summit sells them any longer (or at least didn't last I checked). Might be limited in quantities. If you decide to go a similar route, check the bottom thickness of rad against your lower brackets before purchase. I can't recall exactly why (if I ordered the wrong parts or what) but my lower rad brackets needed enlarged,

[volksworld]

Z10 is there a youtube video of that compressor air hose test ?

[Lee H]

Originally Posted by Robert Bergstrom

Thanks, I will Craig's list the 3 core. It is a good used radiator. Did not want to spend the $$$ for a nice aluminum but will. What is a good brand? Anyone.

Is you current set up running hot? I would think in your neck of the woods a 3 core would do the trick, assuming all other cooling system components are up snuff.

[cdowns]

4 core radiators are very highly overrated the 3core will do the job in 99.9% of the time

[Z10]

Couple of more graphics

Originally Posted by 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!

I purchased this 2 core radiator and have it installed in my 72 cooling a ZZ4 with A/C. Cools like a champ and the tanks are similar to the factory tanks. Also, you'll get better cooling with a 2 core and it's less than $240.

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

Check on my build thread for more photos.

[Robert Bergstrom]

Thanks for the great info. Just like most things in life you need to check the facts and not believe the hype!

[MMiller1050]

Hello,

I bought a 2-row Champion Aluminum radiator and it did not cool my 1979 350 in my C-10 , it did not overheat but ran at the verge of overheating. This was with a stock clutch metal fan with a shroud. I called them and asked them about it and they let me exchange with a 3-row aluminum and it now is running temp-wise where it should.

I have seen many posts that say 2-row is better than 3-row or the same, but the poster did say..hey use what works. For my application the 3-row did better. I am now going to try getting a aluminum shroud with two electric fans as big as I can get that fit properly and see if I can get it running cooler.

Also, Champion Radiators seem to be a good product and have all the accessories I think you will need. If anyone has other vendors of good quality products reply back.

My 2Cents....
MikeM

[mr.mud1]

my 2 cents worth,my 72 big block A/C C-20,built,sold and used hauling a camper in California back and forth to Idaho for the first 25 years of it's life,did so with a 3 row rad.it has tanks that would've accepted a 4 row core,as is common but a 3 row core.i re-cored the rad last year while putting the truck back together,could've bought a 4 row core but left it as a 3 row.it runs like a million bucks with the correct shroud and a new fan clutch,the needle on the guage never gets anymore than about a 1/4 from cold to hot.

[72c20customcamper]

Originally Posted by MMiller1050

Hello,

I bought a 2-row Champion Aluminum radiator and it did not cool my 1979 350 in my C-10 , it did not overheat but ran at the verge of overheating. This was with a stock clutch metal fan with a shroud. I called them and asked them about it and they let me exchange with a 3-row aluminum and it now is running temp-wise where it should.

I have seen many posts that say 2-row is better than 3-row or the same, but the poster did say..hey use what works. For my application the 3-row did better. I am now going to try getting a aluminum shroud with two electric fans as big as I can get that fit properly and see if I can get it running cooler.

Also, Champion Radiators seem to be a good product and have all the accessories I think you will need. If anyone has other vendors of good quality products reply back.

My 2Cents....
MikeM

2 row radiators are not all creates equal. It has a lot to do with the tube width the two row Dewitt’s radiator in my Chevelle uses 1.25 inch thick tubes as apposed to their pro series that are 1 inch . I’m not familiar with Champion’s so I can’t comment on their design .

I have a Cold Case I bought for my 72 C20 with fans and shroud but I’ve yet to put it in the stock 3 row keeps the truck cool even towing .

[MARKDTN]

3 row stock rads are generally plenty for a 350. My '83 K20 with 350/700R4 had a 3-row stock. Never had any problems with cooling. When it sprung a leak I upgraded to a 4-row BB radiator and it has cooled fine too. Ran the stock clutch fan for many years, but have since changed to dual C4 Corvette electric fans. 3 row stock rads may not be enough for a big block though. Had a '77 Pontiac Bonneville with a 350 (Pontiac). Engine died and we had a rusty '72 Grandville with a good 455. Put that in with the stock 3 row and it just would not quite keep it cool in Summer with the a/c on in traffic. Had the 4-row out of the Grandville re-cored and even though it was a shade narrower, it cooled just fine. All of that is with stock radiators. When you go to aluminum it changes everything. As noted above, 2 wide cores can replace 4 cores and do a great job.

[Already Gone]

My 72 C10 350/with 350 trans and factory A/C came with a 3 row rad with 4 row tanks. Recently replaced the engine with a SBC 400 with a .030 bore so 406 but nothing exotic in the engine, in fact flat tappet cam with about 9.2 compression. I went back and forth about cooling then decided to have original rad redone and had it made into a 4 row rad. I also had the heater core recored. Figured the factory knew what they were doing so went that way. No cooling issues for me at all.