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I have read all the cooling threads. This a different twist. I get hotter on the freeway than in the city. I have a mild 350 in a 64. Summitt universal alluminum radiator with a 16" electric fan and a full schroud. I did a little experiment. With the car engine off I flipped my fan on (about 2400cfm) and put my hand on the engine side behind the fan and really felt the fan pulling air strong. I then shut the car electric fan off and put a 20" household fan, a Patton brand, in front of the grille and turned it on high. The fan barely stands, it wants to tip over it is blowing so hard. Then I put my hand on the engine side of the radiator and could hardly feel any air comming thru. That fan took the place of being on the freeway I think. Only 2 things are in the way of the air, 1-the billet grille, 2- the 16" fan. Anybody else try this. No wonder I'm hotter on the freeway. No Air Flow. Any ideas?
 

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Not really sure if that proves anything. I doubt your household fan was blowing 60 plus mph wind. But to open the can of worms again....What tstat if any? LOL And on the freeway aren't you running at a higher RPM and moving water faster? LOL
 

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Well driving down the highway your engine will naturally generate more heat so more airflow through the rad is needed. Your right with your findings as far as the air going through the rad, it's much less efficient trying to push air through than to pull it but it is what it is. Your car will also generate negative pressure behind the radiator when driving that helps with airflow. The fan can't simulate that unless you have one that can move air around the whole car not to mention I bet that air from the fan is only going about 20-25 MPH instead of highway speeds.

Anyway, as far as your problem I would guess that your just not getting enough air through the rad on the highway just like you said. What kind of shroud do you have? Is it solid except where the fan is? If so your only moving a little more air on the highway than you are putting around with the fan running. The fan and shroud could actually be restricting some of the airflow that would happen naturally on the highway. Lots of shrouds have flaps to let extra air flow through when it wants to. You could try and see if your fan is sufficient to keep your car cool without the shroud (mount it right to the rad) and see if you get improvments on the highway. Seems like a pain but it could be the ticket or at least confirm the problem.
 

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How close is the fan to the back of the radiator? This is one of the reasons I don't like an electric fan, out on the highway it becomes a restriction and a hindrance more than a help. Now think about a mechanical fan and shroud that has the fan back from the radiator a good many inches. The free air at highway speed can pass through the radiator unimpeded.

Do another experiment and turn on your electric car fan and place the house fan in front again. I bet it doesn't want to fall backwards anymore. It kind of proves that the electric fans are only beneficial at slow vehicle speeds or idle, at high vehicle speeds when you don't need it and it's not running they're more of a blockage. IMO

If your shroud has the fan wrapped tight and real close to the radiator it can only be expected that it just gets in the way of the free air.
 

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Well driving down the highway your engine will naturally generate more heat so more airflow through the rad is needed. Your right with your findings as far as the air going through the rad, it's much less efficient trying to push air through than to pull it but it is what it is. Your car will also generate negative pressure behind the radiator when driving that helps with airflow. The fan can't simulate that unless you have one that can move air around the whole car not to mention I bet that air from the fan is only going about 20-25 MPH instead of highway speeds.

Anyway, as far as your problem I would guess that your just not getting enough air through the rad on the highway just like you said. What kind of shroud do you have? Is it solid except where the fan is? If so your only moving a little more air on the highway than you are putting around with the fan running. The fan and shroud could actually be restricting some of the airflow that would happen naturally on the highway. Lots of shrouds have flaps to let extra air flow through when it wants to. You could try and see if your fan is sufficient to keep your car cool without the shroud (mount it right to the rad) and see if you get improvments on the highway. Seems like a pain but it could be the ticket or at least confirm the problem.


TODD

just wrote what I would have.... I bet the shroud/fan is restricting the flow at speed... in fact I would surmise the fan opening is such that when the fan is running and you at frwy speed a air block is occurring at the fan..

anyhow

Good luck

Veno
 

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Discussion Starter #6
Veno what do you mean an air block at the fan? On the freeway turning on the fan has no effect on my temp. My fan is mounted about 2" from radiator on the schroud and I just installed 4 flaps from spal on my schroud. Also when I turn on my fan not moving the flaps stay shut. When I put the house fan in front of my radiator engine fan off my 2 flaps on the top of either side of the schroud barely open. And the lower ones stay shut. If I manualy open the top flaps with the house fan I can feel lots of air come out. By the way am I spelling "schroud" right?
 

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the fan does not free wheel.. it turns at the speed it is designed to turn... the fan is pulling all it can... and the fan blades will not speed up from the rush of incoming air... the fan will only pass the amount of air is is designed to move regardless of speed... thats the reason for the flaps....

the air can not escape by the fan... so it creates a dam of air in front...

have you examined the waterflow through the radiator,, is there any bubbles in the radiator? does water have good movement?
 

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Discussion Starter #9
I'll have to dissagree with you veno about the fan not free wheeling. I have a Spal variable speed box. It turns on my fan at a pre determined temp and gradually goes faster and faster till about 200 degress then the fan goes full blast. I have a LED light hooked up to the power lead to the fan. That LED light needs very little votage to turn on. Having said that , I can go on the freeway before the engine reaches that turn on temp and the fan will be freewheeling and my LED light will come on, creating its own voltage to turn on my LED. But about what you said, you are saying that at freeway speeds the only air comming thru the radiator is thru the flaps, is that what you are saying? Could my Billett grill be a restriction?
 

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There has to be another variable here that's not being accounted for.

I have my electric fan mounted only 3/8" from the the radiator surface and don't see the air blockage issue at highway speeds. My cooling issues were at idle speeds, which is why I switched to the electric. I actually used to run too cool at highway speeds and overheat at idle, so it's possible that the additional blockage from the new fan/shroud is "hurting me in a good way" at highway speeds and helping more at idle speeds. The net effect is more stable temperatures across the board.

Could it be fin spacing on the radiator that's blocking air being pushed into the radiator?? Is fin layout different between brass and aluminum rads? I don't know why this wouldn't be a problem when pulling air, but it's possible that the way the radiator is finned is complementing one method of air flow and hindering another.

Just a thought. :)
 

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Maybe the air is going through the radiator so fast it doesn't have time to pick up any heat....

We used a Taurus fan sealed tightly to the radiator in the Durango Deuce. We didn't have any cooling problems at any speed. I did modify the front end to direct more air into the radiator by removing the valence and cutting the license plate area out of the bumper.
My old Beemer is the same way, the faster I go, the cooler it gets.
 

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I bought and installed a big twin electric fan on my car. It ran hot in town and ran hot on the interstate. It had never ran hot on the interstate or even moving. My guess was the same as yours. The fan didn't move enough air at speed and blocked more air than it moved on the interstate.
 

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Or maybe it isnt even the cooling system?? What are your A/F's at part throttle cruising? Happened to me in my Nova, busted out the lap top, seen that at around 65mph on the hwy at that precise vacuum and that precise RPM it was a tad lean. Added a little more fuel and now its fine.
 

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Good point Pwrtrip75, my cruise temp is just a tad higher than idling temp. So I know I probably need more jet, too lazy to mess around with it and and it's only 10° higher and steady. It's not enough to bother me that bad.
 

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your fan is capable allowing 2400cuft. ok let assume it will free wheel... what you think triple the volume? on 2400x 3 =7200cfm per min.. not bad... what about 4 times 9,600cuft per min

just to put things in perspective... the 16" surface area of the fan opening= 1.39sqft..(not including the resistance of the blade nor the reduction of the total surface area.) traveling at 60 miles an hour or a mile per min...equals 7,339cuft of air per min.

If we take the surface area of the radiator as 22x19=418sqin /144" = 2.9sqft..

2.9sqft traveling at 1 mile per min= 2.9 x 5280ft=15,312 cuft per min...

lets say for argument sake the fan only takes off 30% of the total surface area

so if we take the 7339 cuft capable of free flow through a 16" opening and we reduce it by 30% equals 5137.3 cuft per min... but still the fan is spining at max speed to produce 2400cfm....

now if the fan were to shut off and free wheel.... it takes figuring the pitch of the blades, rotational resistance.. yada, yada,

I am not saying this is your problem.. just trying to help...
 

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I don't know why people screw around with electric fans for a street car. They are fine for track duty but for the car that's mostly street driven with occasional track duty, stick to an OEM setup. I have a Alum radiator dual core (3 inch I think) with an OEM shroud and the clutch fan. I never go over 180 - 190 in any weather or any driving speed. It has been proven many time that an OEM setup will be the best way to go with cooling.
 
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