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Cooling troubles.

5K views 34 replies 12 participants last post by  Monzilla 
#1 ·
This car I picked up has a 400 60 over motor with a th350 in it. it only had a 15inch flex fan in it. Do you think twin 9inch elect fans will do a better job of cooling??


Yea I know I had room for 10inchers but I ont wont to send them back. The rad did not have a fan shroud on it either.

Thanks for you input!!
 
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#5 ·
I work in the hot rod cooling business and sorry to say that those 9" fans are not enough . You would have been better off with the 15" fan and a shroud.
Electric fans should cover most of the fins on a radiator. You should be running twin 11" fan on this radiator.
T-stat having one hole is good, but putting another on the other side of the first one also a help. No bigger than 1/8" on either hole.
 
#6 ·
No the twin electrics just don't draw air through enough of the core area to be effective. This would be better served with a single fan of about 15-16 inches at the outlet end of a shroud. That creates a low pressure area when there is little to no forward vehicle movement that draws air across the entire fin surface area.

An engine driven fan would also need a shroud for the same reaasons as stated above. Any shroud should fit tightly against the radaitor, this means a rubber seal of some sort so air leakage is minimized which then forces the fan to find air by way of pulling it through the core.

Keep in mind that holes in the thermostat are just intended to help vent air when filling the system. Too much hole area allows coolant to escape into the radiator when the thermostat is closed, this extends the time it takes to get the thermostat open which of course delays engine warm up.

I'm a big fan of four corner returns and a large capacity heater hose size bypass. Four corner return helps eliminate vapors that are often trapped above the rear cylinder combustion chambers which helps control detonation. The bypass circuit whether used to supply cabin heat or not keeps a large amount of coolant circulating before the thermostat opens. This prevents local hot spots from developing around the exhaust seats and spark plugs while the rest of the engine structure and coolant may be cold. This is a situation that often contributes to the common cracking found around Chevy exhaust seats and ports which is the result of the seat becoming much hotter than the surrounding structure this expands the seat into the still colder structure at some point something's going to give. When the engine is up to temp the return helps moderate the incoming coolant temps that blast against the cylinder walls of 1 and 2. If you have cooling problems it is better to invest in a larger radiator, better shrouding and fans, utilization of an engine oil cooler and if necessary a stand alone transmission oil cooler than it is to not use the external bypass. The built in bypass is a very small player in coolant flows and shouldn't be depended upon to furnish sufficient flow when the thermostat is closed to keep exhaust valve seats in reasonable temperature ranges vis-a-vis the surrounding cast structure.

Bogie
 
#7 ·
Assuming your radiator is 31x19 that's 589 square inches and those 9" fans are covering 254.5 of those or 43 percent of the radiator. Not accounting for the amount of air the fan can move, your effective radiator is now less than half. Two electric fans will cover more area than one bigger one if a rectangular radiator is used. One 19" electric fan is 1190 inches of area covered.
Whether a shroud is used for a mechanical or electric fan the coverage is still 100 percent the surface of the radiator so one is always recommended. Mechanical fans will always pull more air than electric fans however you may be able to get away with the 9" fans if a proper shroud is used but I doubt they can pull enough air to compensate for the smallish size considering the fans will have a larger area to pull air from so the amount of air will still be lower. In conclusion, you will always want to shop for the biggest mechanical fan and proper shroud or the two biggest electric fans and a proper shroud to maximize airflow across the radiator.
 
#8 ·
I have a issue with a chevy s10 v8 transplant and I can tell you a shroud makes a heck of a difference in cooling things and I have not got mine ironed out yet but am close but get a six blade flex fan that will cover as much as possible and a good shroud and you should be golden since you have a bigger size radiator of 19 inches compared to my 16 inch.
 
#9 ·
If you can get a shroud to mount those 2 fans onto so they will be drawing through teh whole radiator they may work. You were correct in getting rid of the flex fan. they are pretty useless. A factory 7 blade fan with a properly designed shroud cant be beat if you have room.
 
#11 ·
As you can see there is not much room to work with. The rad is a 22X16 inchr. Not very big but all you can cram in there!


I pulled it out all ready and thinking of putting them in front pushing and put the fan back in and a alum fan shroud off Amaon. I just hope it works!! Very tight.


Taking it to the Street!!
 
#12 ·
With that setup, you'd prolly be better off with dual 11" SPAL fans. I put this setup in my turbo S-10. It pulls through a front mount intercooler, trans cooler, A/C condenser and stock '86 C4 Corvette radiator and cools just fine in our (SETX) mid-90's and 80% humidity. You can also push the rad further forward by creatively notching the core support and making new mounts. I gained almost 2" by doing this...

Russ
 

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#13 ·
OK so I went on Amazon and orderd a alum fan shroud that looks like it might work. I pulled the two fans off the motor side of the rad and put them in the front. I will put the flex fan back with the shroud aand have the two fans to back it up. What you think? All so got another tranny cooler that dont sit in front of the rad. I put it under it in the air flow. Need to stay away from bumper stops!!




 
#14 ·
I feel like your going backwards man. The electric fans are now a restriction to airflow. Use the shroud and get you a two or four bladed GM fan with the 32 degree pitch as big as you can fit. The GM fans are 19" but can be had in 15" 16" 17" 18" inches as well.
 
#15 · (Edited)
Yeah, the two electric up front are now a restriction to the airflow being pulled from the rear by the mechanical fan, so remove them.

With a rear shroud, do as JohnsonGrass1 suggested or get a 6 or 7 blade clutch fan, Flex-a-Lite sells replacement blades and clutches.

That flex fan you've got pictured is a sure fire loser, eats HP and doesn't move enough air...here is the proof on the HP it is costing you, that particular fan -20HP (copy of magazine article archived at the Cleveland Engines Forum) : Cleveland Photos:

That new tranny cooler isn't going to do much cooling if you've got a high stall converter, that type is meant for mostly stock streetrod type deals...you need a tube and fin or stacked plate type to cool any decent stall converter (2800 stall+), Put one of those 9"-10" electric fans on a tranny cooler, that would be a good place for one and then you could put the cooler almost anywhere, even back above the rear axle or something.
 
#16 ·
Well this sux !! The people I was getting the fan shroud from through Amazon just sent me an Email that its bent to hell and back and it was the last one so its going to be 11-20 before they get any more of them!! :drunk: :smash: :(

O well I can work on the fuel pump harness or the new Pro ratch shifter I just got to replace the mega shifter I have.
 
#17 ·
I have two chevy s 10s with v8 swaps in both and cooling at idle has always been a issue and won't get into writing a book here but do some research and see if you can come up with a plastic shroud you can customize and use your flex fan. On my 86 s 10 I took a 4.3 shroud and had to cut and hack and fit with trial and error but got it done and I am 98 percent good on keeping it cool. Just some more tweaking a few things and I should be good. I only have a 31x16 two row one inch tubes in my 86 s10 and a 29x16 in my 96 and its fine with a oem 180 stat and a 17 inch flex fan on a half inch spacer. It's not pretty looking but it works quite well so far and the shroud was less then thirty shipped. I used a 96 s 10 shroud for a 4.3 for reference.

I bet with a correct shroud you would be golden as you look like you have plenty of radiator. I also stay away from the high flow stats as some times they make things worse then good but as always results will vary build to build. Hope you get it fixed. Awesome car by the way :)
 
#22 ·
NO....You have to do the math correctly for AREA....two 9" fans cover 127.23 square inches of surface....one 15" fans covers 176.71 square inches of surface.
So as you can see - two 9" fans does not equal one 18" fan, it doesn't even equal one 15" fan, in fact it is just slightly less than one 13" fan when you figure area covered in square inches.

Everyone has been telling you that two 9" fans is not likely to get it done....you don't seem to be listening to what is being said....
 
#23 ·
Area of a circle.

A = πr2 = πd2/4

A 9" fan is 63.6 sq inches
A 14" fan is 154 sq inches
A 15" fan is 177 sq inches
A 19" fan is 284 sq inches

2 9" fans is 127 sq inches
2 14" fans is 308 sq inches
2 15" fans is 354 sq inches

Because the radiator is rectangle you can fit two 15" fans and get more area covered than one 19" fan. Even 2 14" fans will cover more area than 1 19" fan.

Thanks for fixing my math errors Eric.
 
#25 ·
No my mind is not made up at all. This hole thing is driving me nuts. Im thinking of making a fan shroud and adding a new six blade fan and leaving one of the 9 inchers in the front of it with a switch so I can turn it on if I wish.
My rad is only 16x22 not much room for side by side fans.
 
#27 ·
Did you build the 400? or was it in the car when you bought it?

The fan on the WP with a shroud should be good to go. I don't hold much faith in electric fans as AM add ons. They don't seem to do as well as the origional with a shroud. Even Henry Ford knew the value of a fan shroud back in the 20's. That's why he put them on his cars.
 
#32 ·
Wrong heads can cause overheat problems on SB400. I've seen it too many times. Installing a set of heads from any other SBC without drilling the steam ports is a recipe for disaster in the cooling of it. Or using head gaskets not for a SB400 can block the steam ports, causing the same troubles.
 
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