Big block cooling issues

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Craig Burriss

Craig Burriss

FABO Gold Member
FABO Gold Member
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Hey guys, now that I’ve been putting miles on my Duster, I’ve found that it doesn’t like the summer heat of Georgia. When I’m doing 60 and 70 the car stays around 180°, but as soon as I get into traffic it’ll rise up to 220° and sometimes higher. It’s got an iron headed 440 with about 11:1 compression (if calculated correctly), a complete Holley sniper system running 15 base timing and 36 total, a Pro-Flow aluminum water pump housing, a Summit brand radiator with a 2.25” thick core, overall size is 27.5” W, 19” H, 3” D, I have two 10” 1000cfm electric fans attached directly to the radiator that turn on at 180°, I’m not running a thermostat, and I have an old plastic jug zip tied to rad support as a puke tank. No A/C.
I want to make a fan shroud but I can’t find any aluminum sheeting anywhere but at Lowes and they want $60 for the piece I need, and I don’t want to make a shroud if it’s not going to help any.
Is this radiator too thin? Would a shroud make that much of a difference? Should I get an electric water pump? Is Pluto still a planet? I have many questions and just want my car to run cooler.

Any input is greatly appreciated,
Thanks!
 
You're not moving anywhere near enough air at low speeds/stop. Those fans are sissies. You need somewhere around 4k CFM. And run a 180 high flow thermostat.
 
First off, You need to run a High flow 185 Milodon stat or equivalent with a high flow pump! I have no issues with a standard stock setup. Do not forget the basics! I did and learned from my mistakes the hard way!
 
yep, 10" fans are too small. You need at least 12" and try to fit 14".
Here's the results of some tests we did when designing our fan kits.
dual 12" 2800 cfm
single 16" 2600 cfm
dual 10" 1400 cfm.
Doesn't matter what they are rated at, there's not many 10" fans that pull much air unless they have huge motors on them.

Upgrade the fan/shroud combo and that should bring the temps down quite a bit.
 
So a High flow thermostat would cool better than no thermostat at all? I removed my factory style 180° because I thought it would help flow, and it doesn’t take long for my car to get up to temp.
 
Craig Burriss said:
So a High flow thermostat would cool better than no thermostat at all? I removed my factory style 180° because I thought it would help flow, and it doesn’t take long for my car to get up to temp.
Click to expand...


High flow stats are another animal. Yes put one in! Google or better yet go get one and install it. You will see the difference quickly.
 
Coolant needs some time through the radiator to actually cool and work. On hot day it restricts enough to let the radiator work. On cool days it lets you warm up quicker! No stat is just constant flow and no time to cool or warm!
 
Agree on put the thermostat back in.
Agree ditch the 10" fans.

IMHO get a 7 blade OEM fan, space it an inch from the radiator, NO shroud, and see how things go.

Any shroud that is flat will build up pressure at speed and you will have reduced cooling at speed, OEM shrouds have HUGE openings for the fan/ fans and are tapered like a funnel.
 
Dana67Dart said:
Agree on put the thermostat back in.
Agree ditch the 10" fans.

IMHO get a 7 blade OEM fan, space it an inch from the radiator, NO shroud, and see how things go.

Any shroud that is flat will build up pressure at speed and you will have reduced cooling at speed, OEM shrouds have HUGE openings for the fan/ fans and are tapered like a funnel.
Click to expand...

Agree but disagree.

Since going back to a pure stock arrangement with hard 7 blade, correct spacer, shroud and radiator , what a difference! 185 high flow stat and pump just helps more. I dumped the large electric pusher fan altogether and much happier!
 
Getting to 200 or 210 is really not an issue in traffic either. If she drops quickly once moving a bit. You will never see 180 all the time!
 
Craig Burriss said:
Hey guys, now that I’ve been putting miles on my Duster, I’ve found that it doesn’t like the summer heat of Georgia. When I’m doing 60 and 70 the car stays around 180°, but as soon as I get into traffic it’ll rise up to 220° and sometimes higher. It’s got an iron headed 440 with about 11:1 compression (if calculated correctly), a complete Holley sniper system running 15 base timing and 36 total, a Pro-Flow aluminum water pump housing, a Summit brand radiator with a 2.25” thick core, overall size is 27.5” W, 19” H, 3” D, I have two 10” 1000cfm electric fans attached directly to the radiator that turn on at 180°, I’m not running a thermostat, and I have an old plastic jug zip tied to rad support as a puke tank. No A/C.
I want to make a fan shroud but I can’t find any aluminum sheeting anywhere but at Lowes and they want $60 for the piece I need, and I don’t want to make a shroud if it’s not going to help any.
Is this radiator too thin? Would a shroud make that much of a difference? Should I get an electric water pump? Is Pluto still a planet? I have many questions and just want my car to run cooler.

Any input is greatly appreciated,
Thanks!
Click to expand...
ck your . go back to stock. open up front . runn a 3 corr radiator only clean clean. in and out in ok and a ther mo stst man get motor say how hot .. shrould good a glutch fan or a and i say a no thermostst . but u get a block sensor and that will kick on fan ..... u do me this get a thermo stas keek schrould . this will woork
 
charles mill said:
ck your . go back to stock. open up front . runn a 3 corr radiator only clean clean. in and out in ok and a ther mo stst man get motor say how hot .. shrould good a glutch fan or a and i say a no thermostst . but u get a block sensor and that will kick on fan ..... u do me this get a thermo stas keek schrould . this will woork
Click to expand...
What?
 
Craig Burriss said:
Hey guys, now that I’ve been putting miles on my Duster, I’ve found that it doesn’t like the summer heat of Georgia. When I’m doing 60 and 70 the car stays around 180°, but as soon as I get into traffic it’ll rise up to 220° and sometimes higher. It’s got an iron headed 440 with about 11:1 compression (if calculated correctly), a complete Holley sniper system running 15 base timing and 36 total, a Pro-Flow aluminum water pump housing, a Summit brand radiator with a 2.25” thick core, overall size is 27.5” W, 19” H, 3” D, I have two 10” 1000cfm electric fans attached directly to the radiator that turn on at 180°, I’m not running a thermostat, and I have an old plastic jug zip tied to rad support as a puke tank. No A/C.
I want to make a fan shroud but I can’t find any aluminum sheeting anywhere but at Lowes and they want $60 for the piece I need, and I don’t want to make a shroud if it’s not going to help any.
Is this radiator too thin? Would a shroud make that much of a difference? Should I get an electric water pump? Is Pluto still a planet? I have many questions and just want my car to run cooler.

Any input is greatly appreciated,
Thanks!
Click to expand...
RustyRatRod said:
You're not moving anywhere near enough air at low speeds/stop. Those fans are sissies. You need somewhere around 4k CFM. And run a 180 high flow thermostat.
Click to expand...

Yup. Biggest deal is the fan CFM. Absolute minimum I would say is about 3,500 cfm. With only 2,000 cfm you're not moving anywhere near enough air.

Next is a thermostat. You absolutely need one. High flow, standard, whatever. The system was designed for a restriction there, honestly I don't even think high flow 'stats are necessary for most applications if everything else in the system is matched up to work together.

The radiator is fine, as evidenced by the car running at 180° when you're cruising at speed. It's the fans and lack of a thermostat that's hurting you most.

Is this your radiator? Summit Racing® Universal Fit Aluminum Radiators SUM-381328

If it is, then the 22.5" core would lend itself to using a Ford Taurus or Chevy HHR fan. Both are capable of moving enough CFM. The HHR fan is from a 2007? HHR, I think they're a little thinner than the Taurus fans. If you do a search on here for HHR there's a few threads on the installs.
 
72bluNblu said:
Yup. Biggest deal is the fan CFM. Absolute minimum I would say is about 3,500 cfm. With only 2,000 cfm you're not moving anywhere near enough air.

Next is a thermostat. You absolutely need one. High flow, standard, whatever. The system was designed for a restriction there, honestly I don't even think high flow 'stats are necessary for most applications if everything else in the system is matched up to work together.

The radiator is fine, as evidenced by the car running at 180° when you're cruising at speed. It's the fans and lack of a thermostat that's hurting you most.

Is this your radiator? Summit Racing® Universal Fit Aluminum Radiators SUM-381328

If it is, then the 22.5" core would lend itself to using a Ford Taurus or Chevy HHR fan. Both are capable of moving enough CFM. The HHR fan is from a 2007? HHR, I think they're a little thinner than the Taurus fans. If you do a search on here for HHR there's a few threads on the installs.
Click to expand...
That’s very close to what I have. Mine is the SUM-381428. Same core though. I only have a few inches between the radiator and water pump pulley which is why I went with these evidently useless fans. I’ll have to find those fan threads
 
1969383S said:
Coolant needs some time through the radiator to actually cool and work. On hot day it restricts enough to let the radiator work. On cool days it lets you warm up quicker! No stat is just constant flow and no time to cool or warm!
Click to expand...

This old wives' tale keeps resurfacing... generations of people apparently don't understand basic thermodynamics or physics. In a word, it is completely untrue.

The reason for a thermostat is to allow the engine to reach a MINIMUM operating temperature before the 'stat opens. Has absolutely nothing to do with "time in the radiator". If you leave out the thermostat, there is max coolant flow at all times, so the engine will take forever to warm up (and if it gets to 180 or your temp of choice, it means your radiator, fan or water pump is improperly sized for the ambient temp!)
 
DrCharles said:
This old wives' tale keeps resurfacing... generations of people apparently don't understand basic thermodynamics or physics. In a word, it is completely untrue.

The reason for a thermostat is to allow the engine to reach a MINIMUM operating temperature before the 'stat opens. Has absolutely nothing to do with "time in the radiator". If you leave out the thermostat, there is max coolant flow at all times, so the engine will take forever to warm up (and if it gets to 180 or your temp of choice, it means your radiator, fan or water pump is improperly sized for the ambient temp!)
Click to expand...

Yes, the “time in the radiator” deal isn’t a thing. As you say, that’s an old wives tale and something that the laws of thermodynamics don’t bear out. Right with you there.

BUT, that’s not the whole story behind a thermostat. It’s more than just time to reach operating temperature, which becomes evident in cars that don’t have proper cooling at temperature without a thermostat.

Think for a second where the thermostat is. That restriction is backing water up in the block, not the radiator. The radiator has a huge advantage in dissipating heat, it has a large surface area as well as moving air AND coolant. The engine does not, only the coolant moves and the surface area isn’t optimized solely for heat transfer. The thermostat restriction allows more heat to transfer into the coolant in the block. Just think about how long it takes to warm your car up and compare it to how quickly it cools down when you’re moving at speed.

Running without a thermostat is bad, both because it takes longer to warm the engine up, which means it spends more time at lower than ideal operating temperatures which causes engine wear. And it also creates a less efficient cooling system once the engine is at temperature, because the engine isn’t transferring heat to the coolant efficiently. The factory could have made the thermostat 6” wide if it wanted/needed to, it is a restriction for a reason.
 
Still doesn't work that way. The only reason to restrict the velocity of the coolant is to avoid cavitation and turbulence issues. Not heat transfer per se. That is driven by the temperature differential between the hot side and the cold side. The radiator has to be large enough to transfer all the heat between a 180F coolant temp and (say) 100F ambient temp. The cylinder heads run a lot hotter than 180F so they don't need as much surface area.

In fact, if coolant moves TOO slowly then there can be hot spots and localized boiling in the heads - which also reduces the amount of heat carried away!

The only engines I have ever seen that don't run dead cold with the thermostat removed have a secondary disk attached to the moving t-stat element. Old Mercedes diesels, IIRC. This disk opens a bypass when the stat is closed - so the bypass is shut off when the stat is open. With the stat completely removed the large bypass stays open all the time and a big percentage of the coolant flow is diverted away from the radiator.
 
72bluNblu said:
Yes, the “time in the radiator” deal isn’t a thing. As you say, that’s an old wives tale and something that the laws of thermodynamics don’t bear out. Right with you there.

BUT, that’s not the whole story behind a thermostat. It’s more than just time to reach operating temperature, which becomes evident in cars that don’t have proper cooling at temperature without a thermostat.

Think for a second where the thermostat is. That restriction is backing water up in the block, not the radiator. The radiator has a huge advantage in dissipating heat, it has a large surface area as well as moving air AND coolant. The engine does not, only the coolant moves and the surface area isn’t optimized solely for heat transfer. The thermostat restriction allows more heat to transfer into the coolant in the block. Just think about how long it takes to warm your car up and compare it to how quickly it cools down when you’re moving at speed.

Running without a thermostat is bad, both because it takes longer to warm the engine up, which means it spends more time at lower than ideal operating temperatures which causes engine wear. And it also creates a less efficient cooling system once the engine is at temperature, because the engine isn’t transferring heat to the coolant efficiently. The factory could have made the thermostat 6” wide if it wanted/needed to, it is a restriction for a reason.
Click to expand...


THIS^^^^^^^^^^^

IF you can get the engine up to temp fairly quickly, IF you can even get some temp in it, IF you need a defrost and you can get enough heat in the engine to do it, IF you can control engine temp in all conditions and climes, you can leave the thermostat out.

I tried. I couldn’t get any temp in the engine. On an 85 degree day I could barely get the temp gauge to 120. Driving on the same day and it dropped down to 110. It hit 130 waiting for a train that was 20 minutes long, and by that time of day it was probably 90 or 92.

So I run a thermostat just to A) get some temp in the engine so I can have heat and defrost and B) so I can control the temp. It’s hard to tune with engine temp all over the place.
 
Would anyone happen to know the dimensions of the Chevy HHR fan? It looks promising.
I guess I’ll add a thermostat to my parts list too
 
yellow rose said:
THIS^^^^^^^^^^^
So I run a thermostat just to A) get some temp in the engine so I can have heat and defrost and B) so I can control the temp. It’s hard to tune with engine temp all over the place.
Click to expand...

I agree completely. I didn't bother commenting (B) because of course without the temperature regulating device (thermostat) there is no regulation :)
 
DrCharles said:
Still doesn't work that way. The only reason to restrict the velocity of the coolant is to avoid cavitation and turbulence issues. Not heat transfer per se. That is driven by the temperature differential between the hot side and the cold side. The radiator has to be large enough to transfer all the heat between a 180F coolant temp and (say) 100F ambient temp. The cylinder heads run a lot hotter than 180F so they don't need as much surface area.

In fact, if coolant moves TOO slowly then there can be hot spots and localized boiling in the heads - which also reduces the amount of heat carried away!

The only engines I have ever seen that don't run dead cold with the thermostat removed have a secondary disk attached to the moving t-stat element. Old Mercedes diesels, IIRC. This disk opens a bypass when the stat is closed - so the bypass is shut off when the stat is open. With the stat completely removed the large bypass stays open all the time and a big percentage of the coolant flow is diverted away from the radiator.
Click to expand...

You're wildly oversimplifying, as most people do. The cooling system is a complex system, and thermodynamics is not a science to be taken lightly. I have years of studying it and an engineering degree, and I'm here to tell you it's not so simple as you're making it. Even after all the time I spent studying it I would not consider myself an expert in it.

Yes, coolant can move too slow which can cause localized boiling which is bad. But that is also controlled by the pressure in the system. Unlike the radiator, which has a lot of built in restriction because of the size of the tubes, the passages of the engine are large. Transfer only takes place where the water is directly in contact with the walls, large cavities don't transfer heat directly to the water in the middle. Turbulence does effect heat transfer too, pretty much all of this stuff is designed assuming you have laminar flow. That's not always true, but that's the assumption and a lot of turbulence changes all of the equations. Cavitation would happen in the water pump, not in the block. The temperature differential between the block and the coolant is higher, which does improve heat transfer, but the surface area and the large cavities are a disadvantage.

The cooling system was designed originally with all of these things in mind. Including the amount of restriction at the thermostat. Yes, it's silly to say that water going through the radiator too fast is an issue. Mostly because of the design of the radiator itself and the fact that it's exchanging both coolant and air. But that also doesn't mean that the thermostat doesn't need to be there for more than initial warm up. It would be easy to make the thermostat orifice larger, it's smaller than the passages on both sides of it. And it is that way for a reason.
 
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I think for me to be able to run a shroud, I'm going to have to cut up my radiator support. With the radiator pushed all the way forwards, I have about 2" from the radiator to the water pump pulley bolts. The shroud/fan assembly that I am looking at is 4.5" thick! The only way that would fit is if I heavily modified my radiator support or removed my water pump and went with a electric pump mounted somewhere else.
Here's what I'm considering
Derale High-Output Dual RAD Fan and Shroud Kits 16830
IMG_5443.jpg
 
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