Fan shroud size vs fan blade

[Ken Hayes]

Fan should be 1" less than the shroud diameter. So if you took a compass and drew a 4" circle and drew a 2" circle inside of it, that would equal 1" clearance at the tip of any blade. So if your blade is 19" and your shroud is 21" your in like flint. Just remember the fan should extend into the shroud at least 1".

Another thing you can do is put a panel on your radiator support to block the open space and force the air through the radiator. www.undercoverinnovations.com is where I got mine.