Radiator Size ????

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Scatpack1

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I have a Demon with a 340 stroked to 408 CI sitting in my garage.
What would you think would be the minimum radiator capacity to keep running/cruising temperatures down?
It has what looks to be a six cylinder size aluminum 3 row radiator in it now. It is constantly getting hot when driving. This is an x race car, I assume the prior owner left the small radiator in it from when he drag raced it. I may need to get another radiator, but don't want to buy it twice, if that makes sense. What do you guys think? I have always ran big block cars and this is my first small block.
Car has an electric fan set to come on at 180*. No fan shroud, but an aluminum plate that does not look to me like it would work very efficiently.
 
As big a two row high quality aluminum radiator you can stand with 1.25" or 1.5" flues. Like maybe a Cold Case or Griffin.
 
IMHO.

get a HP / AC cooling OEM style copper brass new or used OEM radiator.

BUT...

Your fan, pulleys, water pump all have to match the level of cooling you need.

Contact US radiator and talk to them.

Stay away from electric fans and shrouds that are close to the back of the rad and parallel to the rad cores.

remember the factory cooled 340s 383s and even 440s in A bodies without any fancy equipment.
 
My theory? Get the biggest dang radiator that will fit between the frame rails. Use a mechanical fan if you have the room, and a shroud. (My 22" was replaced by a high efficiency 28, and my opel has a 31" 454 crewcab dually radiator.)
 
IMHO.

get a HP / AC cooling OEM style copper brass new or used OEM radiator.

BUT...

Your fan, pulleys, water pump all have to match the level of cooling you need.

Contact US radiator and talk to them.

Stay away from electric fans and shrouds that are close to the back of the rad and parallel to the rad cores.

remember the factory cooled 340s 383s and even 440s in A bodies without any fancy equipment.
426 Hemis, too.
 
Get an alum rad. All else being equal, they cool better than copper/brass. BEFORE fitting it, I would cut open the old rad & check for blocked tubes. Blocked tubes indicates trash coming from the block/heads & will only block up a new rad unless you use a filter in the top rad hose to catch the trash.
 
Make sure your radiator is flowing Air. I had a large Becool radiator that the tubes were expanded round. The radiator would flow water great but did not flow air. It was out of a race car I bought. The radiator either froze due to water left in it. Or was installed behind a engine that was hot and blew a head gasket. After fighting the overheating a discovered the issue. I would have never found it but I was next to the car and felt low air flow with the fan on.

It was large Be cool with twin fans picture below in the orange car.

The second picture is a 408 with a 557 mech cam. Barracuda with AC and a factory radiator. It runs very cool on the 100 degree days. Any good radiator with the engine and cooling working properly should run cool under normal operating conditions. Our stroker big block has a 22 inch rad. As does my friends Blown Hemi car.

Yes aluminum radiators are good but remember to run the proper coolant and also replace your heater core with a aluminum replacement.

The pink doesn't like copper brass with lead. And the green doesn't like the aluminum. Look at and old timing cover that sat with green coolant for a long time. White crust will form.

batten2.jpg


100_0035 (3).JPG
 
Get an alum rad. All else being equal, they cool better than copper/brass. BEFORE fitting it, I would cut open the old rad & check for blocked tubes. Blocked tubes indicates trash coming from the block/heads & will only block up a new rad unless you use a filter in the top rad hose to catch the trash.
Aluminum only has about 60% of the thermal conductivity of copper.
 
Rust inhibitor and coolant can be two separate things.
 
I have a Demon with a 340 stroked to 408 CI sitting in my garage.
What would you think would be the minimum radiator capacity to keep running/cruising temperatures down?
It has what looks to be a six cylinder size aluminum 3 row radiator in it now. It is constantly getting hot when driving. This is an x race car, I assume the prior owner left the small radiator in it from when he drag raced it. I may need to get another radiator, but don't want to buy it twice, if that makes sense. What do you guys think? I have always ran big block cars and this is my first small block.
Car has an electric fan set to come on at 180*. No fan shroud, but an aluminum plate that does not look to me like it would work very efficiently.

I‘m not sure why you are asking about the minimum radiator size you can get away with, because that‘s a bad rabbit hole to go down.

As has been said, get the biggest TWO CORE radiator you can get in there. Two big cores will out cool 3 or 4 smaller cores all day long.

Then you should be buying a high flow water pump. Flow kooler or Milodon will work.

Then you should be using a high flow thermostat. The best out there (and it ain’t cheap but worth every penny) is the Stewart Components thermostats. They are second to none.

And then, as pointed out above you need to get the water pump speed correct. Never and by never I mean never ever slow the water pump down to less that crank speed (under driven). You may save 2 HP but you’ll lose 12-15 HP because you can’t control engine temperature on hot days. And that makes the same engine much more sensitive to detonation.

So, a big two core radiator with a high flow pump and thermostat and turning the water pump at least crank speed (overdriving the pump is even better unless you are shifting at 8500 plus and then you need to worry about blowing the fan apart…unless you have an electric fan) and you can drive through downtown hell on the hottest summer day in slow traffic and your engine temperature will be under control.
 
IMHO.

get a HP / AC cooling OEM style copper brass new or used OEM radiator.

BUT...

Your fan, pulleys, water pump all have to match the level of cooling you need.

Contact US radiator and talk to them.

Stay away from electric fans and shrouds that are close to the back of the rad and parallel to the rad cores.

remember the factory cooled 340s 383s and even 440s in A bodies without any fancy equipment.
I can’t agree more with going OEM. My M-Code ‘Cuda ran less than 190 degrees in 90 degree weather and I’m in Charlotte NC.
 
Here's the 22" Champion rad and fans I use in my 72 Demon (avatar) with the 408 (360-based). The fans/shroud cover it completely as you can see. I blocked off the little sections on the sides or anywhere else air could get pulled in without coming through the rad.

I've said it before - I drive it without issue on the street. Good example was the Woodward Dream Cruise (crawl?) last summer idling for about 30-40 min and went maybe 100 yds in that time in the 90 degree heat. Both fans were singing away...peaked at about 200 on the temp gauge. As soon as the traffic cleared and we could move, it dropped backed to its more normal 175-ish and I flipped off 1 fan which is how I usually run.

As others have said, you can get a prod system to work too. I didn't go that route and am happy with mine. Just showing you one system that seems to work.
20201206_141410.jpg


20201206_141928.jpg
 
Here's the 22" Champion rad and fans I use in my 72 Demon (avatar) with the 408 (360-based). The fans/shroud cover it completely as you can see. I blocked off the little sections on the sides or anywhere else air could get pulled in without coming through the rad.

I've said it before - I drive it without issue on the street. Good example was the Woodward Dream Cruise (crawl?) last summer idling for about 30-40 min and went maybe 100 yds in that time in the 90 degree heat. Both fans were singing away...peaked at about 200 on the temp gauge. As soon as the traffic cleared and we could move, it dropped backed to its more normal 175-ish and I flipped off 1 fan which is how I usually run.

As others have said, you can get a prod system to work too. I didn't go that route and am happy with mine. Just showing you one system that seems to work.
View attachment 1716055456

View attachment 1716055488

Are those the contour fans?? I went down a rabbit hole with an electric water pump and I think I pooped the bed on that deal. Time will tell. It may end up being a pump just to dyno SB Chrysler stuff.

Either way, electric or mechanical pump I want to go to an electric fan. That’s why I’m asking.
 
Do a search on FABO for "overheating"

Then come back and tell me what they have in common.
 
Do a search on FABO for "overheating"

Then come back and tell me what they have in common.

Yeah, I know. I’m pleading temporary insanity.
Sometimes I go down the rabbit hole so far I need help getting out.

I suspect this is going to be one of those times.

One thing to note about the electric water pump is the size of the impeller. The Moroso I have measures .330 and it flat, while the high volume Milodon I have measures .625 (almost double) at the edge and it tapers larger to follow the volute.

Plus, Moroso with their loosey goosey tolerances have the impeller .070 away from the body. So I’m going to machine .060 off the impeller snout to close that gap to .010 to help with exit losses there.

The fitting for the suction (lower) hose goes from 1.250 I.D. to 3/4 inch!!!! Horrible. And where the fitting screws in, there was a shelf (for lack of a better term) that covered half of that hole.

So I bored out the fitting to about .820 and cleaned up the shelf in the body and at least you can see some of the impeller looking through the hole.

I called Meziere on Thursday and talked to one of their guys. That was eye opening for sure.

He said the owner has a BBC SG car that they test with. He uses their 55 GPM pump. That’s free flow. Then they hooked up a flow meter to the system and in actual use that 55 GPM pump only flowed 27 or 28 GPM!

What does that mean if you start with a 32 GPM pump? I can’t say but if it only loses 20% of its free flow you are down to about 25 GPM.
 
Are those the contour fans?? I went down a rabbit hole with an electric water pump and I think I pooped the bed on that deal. Time will tell. It may end up being a pump just to dyno SB Chrysler stuff.

Either way, electric or mechanical pump I want to go to an electric fan. That’s why I’m asking.
I actually ordered the Contour fans, a BeCool set, a Dorman set, and a Jeg's set. I tried them all for fitment to the rad. The best was the Jeg's #555-52115 which are actually Maradyne fans. It really covers a lot of the rad surface area and has the little rubber flaps where it doesn't to allow airflow. So that's what I used and sent the others back. I like the Contour since it's a production car unit but with my 22" rad, it was too wide and would have had fans covering the rad support and not as much on the rad. I can say if you have the hood open and the fans on, there's a lot of air/heat blowing at you!

FWIW - I use the Milodon hi-volume #16250 water pump.

I'm sure there are many ways to make a system that works. This is just what I did.
 
As has been said, get the biggest TWO CORE radiator you can get in there. Two big cores will out cool 3 or 4 smaller cores all day long.

And then, as pointed out above you need to get the water pump speed correct. Never and by never I mean never ever slow the water pump down to less that crank speed (under driven). You may save 2 HP but you’ll lose 12-15 HP because you can’t control engine temperature on hot days. And that makes the same engine much more sensitive to detonation.

So, a big two core radiator with a high flow pump and thermostat and turning the water pump at least crank speed (overdriving the pump is even better unless you are shifting at 8500 plus and then you need to worry about blowing the fan apart…unless you have an electric fan) and you can drive through downtown hell on the hottest summer day in slow traffic and your engine temperature will be under control.

Yeah, not all that is true.

Two cores with big tubes will not always out cool 3 cores with smaller tubes. You actually have to do the math, figure out the surface areas, flow rates, number of fins, all of that. There are 3 core radiators out there that will out cool large tube 2 cores. The factory ran 3 core radiators too!!!

There are two major gimmicks in radiators at the moment. One is more cores, the other is big tubes. The companies that just add cores will sell you a 4 core radiator and say it's the best, despite the fact that the air going through the radiator is slowing down and heating up, making the additional cores less efficient as they go. The companies that add giant tubes will say they're best, despite the fact that they may actually be losing surface area, or that the large tube will not cool as efficiently all the way across that larger cross section. Both styles can become less efficient as things get extreme.

Bottom line is, "bigger tubes!" is as much a gimmick as "more cores!" if you're not actually checking the numbers and doing the math. A well set up 3 core can out cool a poorly set up large tube 2 core, and a well set up large tube 2 core can out cool a poorly set up 3 core. I would stay away from 4 cores just because of the overall thickness of the radiator, which can also be an issue with the really large tube 2 core radiators. It does have to fit in the car.
Do a search on FABO for "overheating"

Then come back and tell me what they have in common.

Easy, poorly set up cooling systems for both electric and mechanical systems. Want the Reader's Digest version?

-Electric fans that don't move enough air (expensive does not equal good)
-Mismatched pulley's under driving the water pump
-Wrong water pump for the pulley ratio (factory ratio .95:1 pumps had 8 vanes, factory 1.3:1 ratio pumps had 6)
-Poorly controlled electric fans (manual switches and temp probes are not great)
-No shroud (mechanical or electric), fan not covering enough surface area or pulling across the entire radiator

And you can even throw in mechanical fans that are too small or don't have the right number/shape of blades (they're designed to work at a certain RPM), electric fan systems with wiring that's too small or with alternators that can't provide enough juice to meet the specs, plugged tubes, radiator hoses sucking closed, thermostats not opening correctly (or removed altogether), internal engine passage issues, etc, etc.

But people that slapped together a poorly thought out electric fan SYSTEM will say electric fans suck. And people that spent a brick on a fancy radiator will say cheap radiators can't work either.

I actually ordered the Contour fans, a BeCool set, a Dorman set, and a Jeg's set. I tried them all for fitment to the rad. The best was the Jeg's #555-52115 which are actually Maradyne fans. It really covers a lot of the rad surface area and has the little rubber flaps where it doesn't to allow airflow. So that's what I used and sent the others back. I like the Contour since it's a production car unit but with my 22" rad, it was too wide and would have had fans covering the rad support and not as much on the rad. I can say if you have the hood open and the fans on, there's a lot of air/heat blowing at you!

FWIW - I use the Milodon hi-volume #16250 water pump.

I'm sure there are many ways to make a system that works. This is just what I did.
Exactly!

The OE Ford Contour fans work best on a 26" radiator. I love mine, my car will run at whatever temperature I program the fans for as long as the thermostat matches that temp. And I just run a standard thermostat, the 8 vane pump correct for my pulley ratio, and a Champion 26" 3 core radiator. There are a lot of ways to set up a good system, and even more ways to set up a bad one.
 
Make sure your radiator is flowing Air. I had a large Becool radiator that the tubes were expanded round. The radiator would flow water great but did not flow air. It was out of a race car I bought. The radiator either froze due to water left in it. Or was installed behind a engine that was hot and blew a head gasket. After fighting the overheating a discovered the issue. I would have never found it but I was next to the car and felt low air flow with the fan on.

It was large Be cool with twin fans picture below in the orange car.

The second picture is a 408 with a 557 mech cam. Barracuda with AC and a factory radiator. It runs very cool on the 100 degree days. Any good radiator with the engine and cooling working properly should run cool under normal operating conditions. Our stroker big block has a 22 inch rad. As does my friends Blown Hemi car.

Yes aluminum radiators are good but remember to run the proper coolant and also replace your heater core with a aluminum replacement.

The pink doesn't like copper brass with lead. And the green doesn't like the aluminum. Look at and old timing cover that sat with green coolant for a long time. White crust will form.

View attachment 1716055388

View attachment 1716055389
I remember you posting about that once before. That's an issue people would very likely overlook when looking for reasons why one is running hot. Easy to see how it could impede airflow. That's why most these radiator companies recommend a two row with BIG tubes, because stacking more rows in only cuts down on air flow.
 
Yeah, not all that is true.

Two cores with big tubes will not always out cool 3 cores with smaller tubes. You actually have to do the math, figure out the surface areas, flow rates, number of fins, all of that. There are 3 core radiators out there that will out cool large tube 2 cores. The factory ran 3 core radiators too!!!
That's true. But for most street applications it works well. I had a nice aluminum 3 row in Vixen for a while. I couldn't STAND how ill fitting it was. I was able to get a factory three row from a good member here that was in almost new condition and it cools every bit as good and fits SO much better. But you're right. The two row theory isn't right for every single thing.
 
Yeah, not all that is true.

Two cores with big tubes will not always out cool 3 cores with smaller tubes. You actually have to do the math, figure out the surface areas, flow rates, number of fins, all of that. There are 3 core radiators out there that will out cool large tube 2 cores. The factory ran 3 core radiators too!!!

There are two major gimmicks in radiators at the moment. One is more cores, the other is big tubes. The companies that just add cores will sell you a 4 core radiator and say it's the best, despite the fact that the air going through the radiator is slowing down and heating up, making the additional cores less efficient as they go. The companies that add giant tubes will say they're best, despite the fact that they may actually be losing surface area, or that the large tube will not cool as efficiently all the way across that larger cross section. Both styles can become less efficient as things get extreme.

Bottom line is, "bigger tubes!" is as much a gimmick as "more cores!" if you're not actually checking the numbers and doing the math. A well set up 3 core can out cool a poorly set up large tube 2 core, and a well set up large tube 2 core can out cool a poorly set up 3 core. I would stay away from 4 cores just because of the overall thickness of the radiator, which can also be an issue with the really large tube 2 core radiators. It does have to fit in the car.


Easy, poorly set up cooling systems for both electric and mechanical systems. Want the Reader's Digest version?

-Electric fans that don't move enough air (expensive does not equal good)
-Mismatched pulley's under driving the water pump
-Wrong water pump for the pulley ratio (factory ratio .95:1 pumps had 8 vanes, factory 1.3:1 ratio pumps had 6)
-Poorly controlled electric fans (manual switches and temp probes are not great)
-No shroud (mechanical or electric), fan not covering enough surface area or pulling across the entire radiator

And you can even throw in mechanical fans that are too small or don't have the right number/shape of blades (they're designed to work at a certain RPM), electric fan systems with wiring that's too small or with alternators that can't provide enough juice to meet the specs, plugged tubes, radiator hoses sucking closed, thermostats not opening correctly (or removed altogether), internal engine passage issues, etc, etc.

But people that slapped together a poorly thought out electric fan SYSTEM will say electric fans suck. And people that spent a brick on a fancy radiator will say cheap radiators can't work either.


Exactly!

The OE Ford Contour fans work best on a 26" radiator. I love mine, my car will run at whatever temperature I program the fans for as long as the thermostat matches that temp. And I just run a standard thermostat, the 8 vane pump correct for my pulley ratio, and a Champion 26" 3 core radiator. There are a lot of ways to set up a good system, and even more ways to set up a bad one.


Right. I’m talking about a correctly engineered two core.

I haven’t been to a circle track in a while (because I’m not a fan of that and unless I’m there to tune something I don’t go) but virtually every car that doesn’t have issues under caution (where far more cooling issues occur) runs an overdriven water pump and a two core radiator. And they have a tune up that isn’t stupid. And if they really have their poop in one group they are running vacuum advance.

And the opposite is true. The cars that overheat under a yellow have multiple smaller cores, double and triple pass junk **** and underdriven water pumps. And if you dig in, you’ll see they don’t have a vacuum advance, a locked out distributor and some crazy thing like 32 total, that even running at 3k is probably retarding some.

So the answer always is buy the biggest two core radiator that will fit (one that is correct designed), overdrive the water pump and get the tune up correct.

You also have to consider what happens when the cores are smaller. How much more restriction does that add to the system? I don’t know but someone with good math skills could probably get close.

If a 55 GPM water pump loses near 50% of its capacity with a high flow radiator, how much more restriction does a 3 or 4 core add?? Then add in the horrible double pass or worse yet the hideous triple bypass.

You add so much restriction to the system you still don’t have the coolant flow.
 
The radiator is a resistor to air flow. Think about that when you're looking at getting electric fans. If the fans are weak, they will stall and not pull much air.
 
Right. I’m talking about a correctly engineered two core.

I haven’t been to a circle track in a while (because I’m not a fan of that and unless I’m there to tune something I don’t go) but virtually every car that doesn’t have issues under caution (where far more cooling issues occur) runs an overdriven water pump and a two core radiator. And they have a tune up that isn’t stupid. And if they really have their poop in one group they are running vacuum advance.

And the opposite is true. The cars that overheat under a yellow have multiple smaller cores, double and triple pass junk **** and underdriven water pumps. And if you dig in, you’ll see they don’t have a vacuum advance, a locked out distributor and some crazy thing like 32 total, that even running at 3k is probably retarding some.

So the answer always is buy the biggest two core radiator that will fit (one that is correct designed), overdrive the water pump and get the tune up correct.

You also have to consider what happens when the cores are smaller. How much more restriction does that add to the system? I don’t know but someone with good math skills could probably get close.

If a 55 GPM water pump loses near 50% of its capacity with a high flow radiator, how much more restriction does a 3 or 4 core add?? Then add in the horrible double pass or worse yet the hideous triple bypass.

You add so much restriction to the system you still don’t have the coolant flow.

Yeah, it's not that simple. Not at all.

Your anecdotal evidence about "cars that overheat under yellow" gives 4 different variables, any ONE of which could be the source of their overheating issue. And for many of them, it probably isn't the radiator at all. Because here's the thing, cars that overheat when sitting still usually have a fan problem, not a radiator problem. If they're staying cool at speed their radiator is fine, they're not moving enough air through the radiator sitting still. And of course, using a race car example is usually a bad choice, because people do really specific things that work well for their type of racing that will not hold up for a street driven car anyway.

The problem is that none of the aftermarket radiator companies, or the factory ones for that matter, publish enough of their specs to do a full mathematical calculation on them. This is on purpose.

A radiator is just ONE part of the whole cooling system. The water pump, the pulley ratio's, the CFM of air the fans can flow, the rate of coolant circulation, horsepower of the engine, ALL of that matters. If you look at the factory cars you see Ma Mopar had two major configurations, AC and non-AC. The non-AC cars got a .95:1 water pump pulley ratio (technically under driven!) and the HD 8 vane water pump (and usually a 2 core radiator). The AC cars got a 1.3 or 1.4:1 water pump pulley ratio, the standard 6 vane water pump, and a 2 or 3 core radiator depending on the engine, year, model, etc. Why did they change the water pump? Wouldn't more water flow be better for the AC cars that needed more cooling? Well, they wanted to increase the air circulation and keep the water circulation closer to the same. Overdriving the water pump was to speed up the fan, to move more air. But they downgraded the water pump, to keep that rate similar as the other set up. Almost like there was an ideal water circulation rate for that system and pump.

It's a cooling system, and you can't have a "properly engineered" radiator unless it was engineered specifically for all of the specifications of that particular car. Since we don't have unlimited ability to select pulley ratios, water pump output volumes, fan CFM etc there's gonna be a limit to what works well. And the "biggest two core radiator" that will fit isn't the only answer. Or even necessarily the right answer.

I run a 3 core with Ford Contour electric fans. Has worked great for me, even stuck in traffic in 110°F weather. I wouldn't trade it for a 2 core just because someone says bigger tubes are better.

The radiator is a resistor to air flow. Think about that when you're looking at getting electric fans. If the fans are weak, they will stall and not pull much air.

Fan CFM has to be matched to the rest of the system. If you replace a mechanical fan that has an output of 4,500 cfm with an electric fan, you're gonna need an electric fan that can pull 4,500 cfm or so if you want to have a decent chance at it working. It's not the fan stalling that's the issue, it's usually just a lack of output. People seem to have a habit of picking fans because they have a cool aftermarket name or cost a certain amount instead of picking them by the CFM they can move. There are plenty of really expensive aftermarket electric fans that don't move enough CFM for these cars.
 
The contact area of the fin to the tube is the only real point of heat transfer.

If it is small or fewer then you will have less cooling ability. So a 2 core rad with 10 fins per inch and the same 2 core but with 20 fins per inch. The 20 fin per inch will cool better.
 
Fan CFM has to be matched to the rest of the system. If you replace a mechanical fan that has an output of 4,500 cfm with an electric fan, you're gonna need an electric fan that can pull 4,500 cfm or so if you want to have a decent chance at it working. It's not the fan stalling that's the issue, it's usually just a lack of output. People seem to have a habit of picking fans because they have a cool aftermarket name or cost a certain amount instead of picking them by the CFM they can move. There are plenty of really expensive aftermarket electric fans that don't move enough CFM for these cars.
Slowly block off the electric fan and it will start to slow down. That is a condition of stall.
And what does it do when it starts to stall? Yeah, you guessed it, it's output is reduced.
So please, don't go telling me what's- what. ok?
You can talk all the CFM you like but under how many inches of h2o is that CFM being achieved?
No point having a fan that has 4500 CFM free flow, just to find it only has 1000CFM once it's put up against the radiator.
I'm not going to bother getting into the nuts and bolts of cooling systems and how to effectively set them up, because this place does not pay my bills, but I can see from this thread that most people have zero idea about it.
For those who want to get an idea, look at late model OEM stuff.
 
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For those who want to get an idea, look at late model OEM stuff
I agree there BUT... look at the size of the radiator for a V6 as compared to that of a 60s 70s V8. The V6 is huge compared.
 
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