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happy belated new year!!!

i have two new cooling fans i am going to install as sucker fans and am curious as to the better mounting method. should i mount them on rails or fabricate a shroud that would cover the entire back side of the radiator?

i do not want to mount the fans with any "through the core" fastening devices (much too easy to do).

if the shroud is the better route, about how close to the radiator can the shroud be, the greater the distance between the radiator face and the shroud results in air being pulled over a greater surface area of the radiator. but then the radiator must be leaned forward to a greater degree which directs the airflow less efficently (no hood vents).

without a shroud, it would seem that you get cooling air being passively forced through the radiator by the cars movement and by fan assist. whereas with a shroud, the passive airflow would be substantially, if not totally, reduced.


thoughts, opinions, suggestions????

thanks in advance

nazgul.
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I've already gone through this with 6018.

I had a custom radiator built, with a 1" thick shroud on the back side. I can mount the radiator straight up in the oem configuration IF I use the Spal medium duty fans, which are relatively thin. If I opt for the heavy duty fans, I'll have to lay the radiator down a small amount, because the fans hit the headlight bar. The thicker heavy duty fans also hit the inner fender walls down low. I purchased both sets of fans, so this is not guess work, this is based on actual trial and error.

I'll be starting with the medium duty fans, and only go to the heavy duty versions if the medium duty fans prove to be inadequate.

cowboy from hell
When installing the dual flexalite fans/shroud unit read up and seem to recall the optimal distance for the fan blade to radiator was a 3/4" gap, which for that unit entailed fabricating some brackets with a stand off and installing a thicker rubber seal around the shroud.

As Larry says the shroud comes into its own at low speed (presuming it is sealed to the radiator) as it forces the fans to pull air through the rad and prevents short circuiting. At high speed (sustained 150+ mph) it can be a detriment as the shroud can restrict air flow as has been discussed previously. Johnny Woods encountered it and overcame it with a neat system of flaps that were forced open by the air pressure at high speed.
As Julian says, I found the flexilite fans and shroud would work perfectly in traffic, but at 150mph (when the engine is building it maximum heat) the car would very quickly overheat because large areas of the radiator where blanked off with the shroud.
I can remember one particular time in France (before I installed my taller 5th gear) I was at the toll both entering a very quite motorway when a Lamborghini Murcielago pulled up along side. I chased the lambo until I was over revving the Cleveland in 5th at 6500 rpm. My friend Tom shouted "look at the temperature gauge" It was nearly off the clock!
I said "F**k me" and Tom said "F**k me"! We could smell the engine over heating even at that speed.

When I got home I cut away all the plastic that formed the corners of the shroud and made some aluminium flaps. These flaps suck down when the fans are on in traffic, and blow open at about 10 mph.

I had no chance of catching the Lambo..
Johnny

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