Another Radiator question

[Rufas]

I have a 1970 GMC with the original 4 core Harrison radiator. The radiator is in good shape. But the Arizona summer temps are typically between 110⁰ and 120⁰. The 4 core isn't happy idling in these temps.

So I'm considering replacing it. I've researched here and now totally confused. There are so many options brass/copper, aluminum, 2 core, 3 cure, 4 core, 5 core, fin spacing and the list goes on and on.

Fit also seems to be an issue, especially the lower rubber radiator pads. What is the best bang for the buck. I'm not crazy rich so my budget is about $500. I'm not worried about keeping the original appearance of the radiator. I just want something that works.

Who has experience with replacement radiators? What style radiator can handle the summer temps here?

TIA

[Stocker]

A four-row in good condition should be able to handle your high Arizona temps, if everything else is up to snuff. Tell us more about your cooling system. Does it have a shroud that fits? And a fan that properly fits the shroud? What type of fan? Is there a coolant recovery tank and a radiator cap for a closed system? A few pics might be helpful.

[RustyPile]

You say the radiator is in good shape?? Before you drop $500 on another radiator, you need to do some troubleshooting.. Things to check/service:

(1) Remove radiator and have it cleaned and pressure tested..
(2) Flush cooling system.
(3) Replace thermostat and coolant.
(4) Check hoses and belts, replace as necessary.
(5) If equipped with a fan clutch, make sure it's operating properly.

The radiator is not the only component in the cooling system. If you arbitrarily just replace it and this is not the problem, you may have just wasted that money. Throwing parts at a problem, hoping something "sticks" is not a wise approach.. Find the root cause of the overheating and repair it properly.

[72SB]

OP. Historically the 4 row radiator was the heavy duty one to have. However, one with 2 rows but 1 1/4"-1 1/2" rows vs 4 smaller ones cools better.

heating up at idle indicates not enough fan and or not the proper shroud for the fan. The 19" 7 blade fan would be what I would get if you have fewer blades than 7. The fan blades should be 1/2 in/out of a fan shroud for it to "pull" air through radiator optimally.

Old radiators may "look" good, but the cores are partially clogged considerably reducing its ability to dissipate heat. Getting them boiled and cleaned is one option but IMHO a 50 year old radiator repair is throwing money at an old part.

If you have an IR heat gun, while truck is at operating temp, scan the front surface of radiator to confirm it is = temp all around. Often the lower section clogs and is basically not doing anything reducing the cooling ability considerably.

Replacement radiators, well you will get several opinions. Typically, you get what you pay for. The higher $ USA made ones, IMHO, are the better ones. With that said I have had a Cold Case in my 67 Camaro for a few years now without issue. The price point of the CC is well within your budget. Four Seasons on the other hand is a high $ very high-quality radiator but would likely be more than your $500 budget, mine was $600 several years ago.

[weq92f]

.

I had the same creeping temps at idle in the heat of summer (100F+) w/AC going full blast. It was an airflow problem, not my copper/brass 4 core original radiator. Fixed it with more airflow.

Have a look at the Champion radiators, CC369 comes to mind, several members here have used them with success.

Hth,

-Kevin

[Dashman]

I would remove your current thermostat, place it in boiling water, and see if it opens all the way. If it's a 195 degree, maybe a 180 degree would be better, or if it's a 195, maybe it's not opening all the way. You either have a condition of too much flow, or not enough coolant flow. The other thing is air flow through the radiator by way of your fan and shroud. Maybe your heat suggests a need for an electric pusher fan. Champion radiators may sound like an American made radiator, but they're made in China. The bungs don't match the specs for 1/2-20 thread. Maybe because their TIG welding process is expanding the bungs. The only aluminum American made radiator that I know of is "Be Cool". ...and coolant can lose it's effectiveness to transfer heat. Good luck, and stay cool.

[72c20customcamper]

Dewitt’s is American made but is way over your budget . The bare direct fit for 67-72 radiator is $859 . I’ve had two in my Chevelle the first got damaged when my neighbors landscaper decided to back into the car with his trailer . Fit finish and function has been perfect past twelve years.

I put a Cold Case in my 72 recently I bought it at the Syracuse nationals about 5 years ago box was stained and frayed but it was too cheap to pass it up fit was spot on can’t say how it cools as I haven’t driven the truck yet

[indymachinist]

I have a champion that started leaking with like 3000 miles on it. I don’t recommend them.

[1970 CST Short Wide]

I have an original 4 core in my 70. I put it in Loooong ago when I had a BB in the Truck,
Worked Perfect. Now I have an LS in the Truck, same Radiator, runs 210 ( That’s where LS Run) all day Long AC or Not. I’d make sure your 4 core is in perfect condition and Keep it

[Rufas]

Originally Posted by 72SB

heating up at idle indicates not enough fan and or not the proper shroud for the fan. The 19" 7 blade fan would be what I would get if you have fewer blades than 7. The fan blades should be 1/2 in/out of a fan shroud for it to "pull" air through radiator optimally.

I think you found my problem, low air flow. I'm running the small Weiand 142 supercharger with serpentine belt pulley system. With the serpentine system I use a reverse rotation water pump and fan. I'm also using the factory shroud. With the supercharger I can't use a fan clutch. With this drive system my fan options are limited. I'm using a 6 blade 18 inch fan. A 19 inch fan is to large for the factory shrould.

To get the fan to clear the supercharger belt I used a 3 inch fan spacer. This unfortunately puts the fan totally inside the shroud. The rear edge of the fan is flush with the shroud rear opening.

The fan itself is 2 inches deep. It appears I need to trim a minimum of 1 inch off of the shroud.

It this works, it's a whole lot cheaper than a new radiator.

Thanks for the info.

[Luke87gt]

I purchased a 3 core aluminum eBay radiator for $130 (China)

Hopefully I won’t be regretting it right away lol

[1970cstblazer]

This may exceed you budget, but I would get your existing unit re-cored. This will hold up better than any new part if the work was done competently.

[Stocker]

Originally Posted by Rufas

I think you found my problem, low air flow. I'm running the small Weiand 142 supercharger with serpentine belt pulley system. With the serpentine system I use a reverse rotation water pump and fan. I'm also using the factory shroud. With the supercharger I can't use a fan clutch. With this drive system my fan options are limited. I'm using a 6 blade 18 inch fan. A 19 inch fan is to large for the factory shrould.

To get the fan to clear the supercharger belt I used a 3 inch fan spacer. This unfortunately puts the fan totally inside the shroud. The rear edge of the fan is flush with the shroud rear opening.

The fan itself is 2 inches deep. It appears I need to trim a minimum of 1 inch off of the shroud.

It this works, it's a whole lot cheaper than a new radiator.

Thanks for the info.

Thank you for the clarification. I was not aware that your supercharger prevented you from using a clutch fan. Hayden makes a low-profile heavy duty fan clutch that might possibly work for you.
It's p/n 2947, versus 2747 which is on my K20. https://www.haydenauto.com/media/548...utch-flyer.pdf

[Rufas]

Originally Posted by Stocker

Thank you for the clarification. I was not aware that your supercharger prevented you from using a clutch fan. Hayden makes a low-profile heavy duty fan clutch that might possibly work for you.
It's p/n 2947, versus 2747 which is on my K20. https://www.haydenauto.com/media/548...utch-flyer.pdf

A low profile fan clutch won't work. Thr fan has to be mounted in front of the supercharger belt. The supercharger belt extends about 3 or 4 inches past the clutch mounting point of the water pump. The other issue is finding reverse rotation fan clutches. I spent hours on the Hayden website researching clutches. I could not find a clutch deep enough to extend beyond the supercharger belt and be compatible with reverse rotation.

Typically most people use electric fans. Going to electric fans is my last resort.

[72SB]

Typo, I meant 18" x 7 blade. I had the asymmetrical 5 blade with my 327 but when I went with a BPE 355, sitting in traffic, I got the temp creep. Put the 7 blade in and that solved the problem.

Cutting the stock shroud down so 1/2 of fan blade depth would allow the fan to pull better. I believe, given the shape of shroud, if you cut off a few inches the opening for fan would get larger. If so a 19" may fit and work better as you also want around 1/2" (vs more) gap to shroud at fan tip.

I would first use an IR gun to confirm there is now blockage (typically on lower area) of radiator causing your temp creep.

[Rufas]

Originally Posted by 72SB

Typo, I meant 18" x 7 blade. I had the asymmetrical 5 blade with my 327 but when I went with a BPE 355, sitting in traffic, I got the temp creep. Put the 7 blade in and that solved the problem.

Cutting the stock shroud down so 1/2 of fan blade depth would allow the fan to pull better. I believe, given the shape of shroud, if you cut off a few inches the opening for fan would get larger. If so a 19" may fit and work better as you also want around 1/2" (vs more) gap to shroud at fan tip.

I would first use an IR gun to confirm there is now blockage (typically on lower area) of radiator causing your temp creep.

I haven't been able to find a 7 blade reverse rotation fan.

My current fan is 18 inches with 1/2 inch shroud clearance.

This morning I removed my factory fan shroud and trimmed about 1 inch off the rear opening. This allowed about 3/4 inch of the fan to extend from the rear of the shroud. The remaining 1 1/4 inch of the fan remains in the shroud.

I tested the temp creep inside the garage. Inside temp was 74⁰. For the first time at idle the temp would reach about 185⁰ and the temps would start dropping to 177⁰. I did this numerous times. Finally some success.

I then took the truck out for a ride. The outside temp was 116⁰. I did a 6 mile ride and made a stop. During that ride the temp slowly increased to 201⁰ when I shut the engine off. Temp was just a steady increase, no temp drops. The speed for this ride was 45 to 55 mph. There was no idling on this portion. What surprised me was the fan noise has deceased..

On the ride home outside temp was 118⁰. When I started the engine the temp was 194⁰. By the time I got home and pulled into the garage the engine temp was 215⁰. Garage temp was still a cool 74⁰. Temp was just a steady increase, no temp drops. The speed for this ride varried between 25 and 45 mph. BTW at the time of posting this the outside temp is 121⁰. Pretty typical for a summer day here in Arizonia.

I used the factory AC on both of these rides.

So what does this mean? I'm still thinking another radiator might fix this issue,

Any thoughts?

[Steeveedee]

It's on the water flow side, it would seem. Do you know if you have a standard thermostat? Not blaming the radiator, yet. My truck ran hot for decades before I got it, and I discovered that a high flow thermostat was the last piece of the puzzle. I had a new aluminum radiator and a recently replaced water pump, good hoses.

[Rufas]

Originally Posted by Steeveedee

It's on the water flow side, it would seem. Do you know if you have a standard thermostat? Not blaming the radiator, yet. My truck ran hot for decades before I got it, and I discovered that a high flow thermostat was the last piece of the puzzle. I had a new aluminum radiator and a recently replaced water pump, good hoses.

I have a high flow thermostat and a Edelbrock high flow waterpump. The engine is a GM crate 350, 9.1 compression, mild cam. Rated at 300hp. Nothing excessive about the engine. With less than 4k miles since installed.

[Stanco]

I don't think you have adequate airflow for Arizona.

Keep in mind that it's harder to pull air through a thick 4 core radiator. If it's plugged with bugs and dirt it reduces airflow even further.

You didn't mention what pulley setup you have. With a mechanical fan with AC you need pulleys that overdrive the fan and water pump. In other words the crankshaft pulley should be larger than the water pump pulley.

A powerful fan and a thin radiator is better in traffic than a thick radiator with a weak fan.

Not all fans are created equal. Which of these three fans do you think would move more air in Arizona traffic?

[72SB]

OP, given the temp you drive in and with AC, 215 showing on temp gauge is pretty normal

Cutting your shroud back did allow your fan to "draw" more through radiator so good deal on that

Did you IR gun your radiator to confirm it does not have and restriction (higher temp typically at bottom because of this)

If you do replace radiator, get one with 2 but large 1 1/4- 1 1/2" tube like Cold Case does.

[Rufas]

Originally Posted by Stanco

I don't think you have adequate airflow for Arizona.

Keep in mind that it's harder to pull air through a thick 4 core radiator. If it's plugged with bugs and dirt it reduces airflow even further.

You didn't mention what pulley setup you have. With a mechanical fan with AC you need pulleys that overdrive the fan and water pump. In other words the crankshaft pulley should be larger than the water pump pulley.

A powerful fan and a thin radiator is better in traffic than a thick radiator with a weak fan.

Not all fans are created equal. Which of these three fans do you think would move more air in Arizona traffic?

With a reverse rotation serpentine belt system, I am limited in choices for fans. I have a Derale 18 inch, 6 blade fan. It's rated at 2000 cfm @ 1000 rpm. Which I think should be adequate flow. The factory shroud opening is 19 inches. Fan is centered and fits nicely in the shroud.

The waterpump pulley is smaller than the crankshaft pulley.

The radiator is clear of bugs, no bent coils. The shroud fits nicely to the radiator.

Photosof shroud and engine bay.

https://www.dropbox.com/scl/fi/a9qcx...91qzmcjiq&dl=0


http://https://www.summitracing.com/parts/DER-17418#overview

[Rufas]

Originally Posted by 72SB

OP, given the temp you drive in and with AC, 215 showing on temp gauge is pretty normal

Cutting your shroud back did allow your fan to "draw" more through radiator so good deal on that

Did you IR gun your radiator to confirm it does not have and restriction (higher temp typically at bottom because of this)

If you do replace radiator, get one with 2 but large 1 1/4- 1 1/2" tube like Cold Case does.

I haven't had a chance to IR the radiator just yet. My IR gun is in our motorhome that is getting serviced this week.

[72SB]

Yeah the reverse rotation thing is a short list of fans. Don't know if this one bolts up to your setup but with your slightly larger shroud opening, the 18.5 x 9 blade would move more air if it bolted up

https://www.summitracing.com/parts/rnb-621-104

[Rufas]

Originally Posted by 72SB

Yeah the reverse rotation thing is a short list of fans. Don't know if this one bolts up to your setup but with your slightly larger shroud opening, the 18.5 x 9 blade would move more air if it bolted up

https://www.summitracing.com/parts/rnb-621-104

That just might work. It's available on Amazon with free returns and free shipping for a dollar more. Summit returns are getting to be a hassle.

My concern is the depth of the mount and at 18.5 inches that's really close to th shroud. Not much room for enginebmovement. With direct drive and 9 blades it must generate a ton of fan noise.

[Rufas]

Originally Posted by 72SB

Yeah the reverse rotation thing is a short list of fans. Don't know if this one bolts up to your setup but with your slightly larger shroud opening, the 18.5 x 9 blade would move more air if it bolted up

https://www.summitracing.com/parts/rnb-621-104

That just might work. It's available on Amazon with free returns and free shipping for a dollar more. Summit returns are getting to be a hassle.

My concern is the depth of the mount and at 18.5 inches that's really close to the shroud. Not much room for engine movement. With direct drive and 9 blades it must generate a ton of fan noise.

Photos of engine bay and shroud. I can't get the direct link to display. So the link is here.

https://www.dropbox.com/scl/fi/a9qcx...91qzmcjiq&dl=0