Originally Posted by matts37chev
how much of the rad. area is cover by the shroud compared to the area open for the fans?
if there is alot of the rad. covered by the shroud, you can cut holes in the shroud for air to blow through, at freeway speed
covering the holes on the outside of the shroud, across the top of the hole, with some thin rubber, will act as a flapper type door for the holes
when the fan kicks on, it will pull the rubber tight up against the shroud, closing the holes, pulling air through the rad. only
I hope this makes sense
This is exactly what I was going to say, I've made fan shrouds from baking pans, and the extra cooling holes will allow more airflow than the fans are capable of on their own, the rubber flaps will still allow the fans to produce a low pressure area behind the radiator when moving slow or sitting still. If there is not some sort of air dam or deflector under your radiator core support, it would be a good idea to add one, this will create a higher pressure area ahead of the radiator, and lower pressure under it, which will enhance airflow through the radiator, based on your speed.
Here's one I did last year:
I/(we) did a fan shroud on my helper's Jeep today, he had his fan attached with those plastic zip ties made for the purpose, and his radiator started leaking because of them, he put a new radiator in it last night, but when I saw that fan attached the same way, I said "NO WAY BUBBA".
This was an 18" x 26" cookie sheet, picked up from the local restaurant supply house, $13.95 + tax,
I cut about 4" out of the middle, I called my buddy Mike to see if he could TIG it back together for us, but he was out of gas and tungstens for his TIG, so I just used the part I cut out to splice it back together, so I just riveted the cut out piece back to both halves. Then I laid the fan in place, marked the mounting holes and cutout for the fan, drilled and cut, then attached the fan.
We used some small holes in the fan shroud to attach it, there were like 12 of them, the perfect size for self tapping screws, assuring this unit would be sturdy and secure.
Then we bent some aluminum strips, (about .040" thick), to attach the shroud to the radiator core's upper and lower frames, and attached them with self tapping screws as well.
It's been on there about a year now, and still cooling very well. We talking about adding some extra cooling holes in that one, but due to the size of the fan vs. the size of the shroud and core, we decided to wait and see if they were needed, and they were not. With that big a fan, and small a radiator core, there wasn't that much room for extra holes anyway.