do I need the fan shroud?


The Grumpy Grease Monkey mechanical engineer.
Staff member
So here is what I got. I have an electric fan on my car. I'm getting a new radiator that is a good bit thicker in the car and the aluminum shroud would require some... Modification to fit. My question is would it be advantageous to modify the shroud over just attaching the fan directly to the radiator? I've seen them run both ways, I just don't want to accidentally lower my cooling ability without the shroud since Arizona isn't exactly forgiving on temperatures. It is significantly easier to just put the fan directly on the radiator, but easy isn't always right. (for anyone wondering, yes I had a champion direct fit, but it started leaking, so now I'm installing a fluidine to resolve that issue.)


the more surface area and coolant volume the radiator has the more potential it has to transfer heat to outside air flow

the shroud definitely helps cooling efficiency, SIGNIFICANTLY,if you don,t have one shop carefully and buy one , if your bucks down visit a salvage yard , measure carefully and buy one used they are commonly under $30
modify it as required to fit



if coolant in the engine gets hotter faster at idle than when your cruising the cause is frequently related to either a lack of air flow (not the correct fan or shroud)
or not enough functional radiator surface area,as the car speed increases it obviously has the effect of increased air flow that results in more efficient heat transfer rates
yes the idea of a larger radiator with increased surface area helps.
most of us are forced due to clearance limitations to select a radiator with specific width and height limitations you can frequently select a radiator thats a bit thicker,
or has a higher fin count per square inch of surface or more efficient inner coolant tube designs.

reading links helps
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The Grumpy Grease Monkey mechanical engineer.
Staff member
building a custom automotive fan shroud ,
trust me here!
Ive done this several times,
card board and duct tape and a yard stick,
and a razor knife are your good friends when making,
and test fitting a pattern, use a motor mount strap to limit engine movement

you'll use for a sheet metal fan shroud, in an ideal design, the fan blades will be about 1/2 way inside the circular opening and the fan shroud will restrict air flow from getting pulled through any route other than though the radiator cooling fins
pop rivets and a sheet metal nibbler are a huge help in fabrication.
but make a carefully test fitted card board pattern first,

1/16" thick (.065) 2' x 3' aluminum sheet is a good place to start

useful related links

watch these linked video's also

mark Bradley posted this info on a torque strap tp limit engine movement ,
to help the fan not hit the fan shroud
To limit the engine rotation under heavy acceleration I built an adjustable torque bar/strap.
I purchased the parts from Speedway Motors.

PartNo, Description, Price

175-6045-LH, 6pc 1/2x20 Jam nut LH, 2.99
175-6045-RH, 6pc 1/2x20 Jam nut RH, 2.99
910-34212-7, 7” Swedged tube, 11.99
175-0305, 1/2” LH heim joint, 5.99
926-10896, Sway bar end link kit, 7.99

I created a plate/arm that bolts to the front of the drivers side cylinder head and extends past the p/s pump. The heim joint connects there and runs directly down to a bracket on the engine cross member. The lower bracket connects with bushings for a sway bar end.
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The Grumpy Grease Monkey mechanical engineer.
Staff member
one of the local guys here in Texas recently installed a thermal clutch fan on a dune buggy he built,
its powered by a salvage yard vortec 350, chevy V8 that probably makes about 350 hp
he was having cooling issues , as the radiator was larger than most average radiators, he originally had used the original 4 cylinder engines fan, a 4 blade fan with the original fan shroud on a non thermal clutch, that the dune buggy was built with, using a directly mechanical linked, fan on the water pump, he used it since the fan fit the shroud, on the original build, he had to move the fan shroud to keep the fan centered in the shroud with the engine upgrade, which significantly boosted power, and than meant the shroud location no longer fit the radiator perfectly, I suggested he ditch the original fan and fan shroud and go with a thermal fan clutch and significantly larger fan with more blades



he thought it looked out of place , as the larger engine water pump center line no longer was centered on the radiator,
but there was no doubt that the change drastically reduced engine heat levels, in fact it now peaks out near 190F, and yeah the fan now was about 30% larger than the original fan and almost the size of the radiator, that measures 21" high and 27" wide, there was zero doubt the original radiator was more than large enough to cool the original engine and a larger fan was not originally required.
I think the main point or info gained is that if you can vastly increase air flow rates, you can also significantly increase the radiators thermal or heat transfer rates and much more rapidly transfer heat out of the coolant in the engine, into the surrounding air.
(even if the fan and shroud are not ideally matched)

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