Heat RISES, bro' ... the HIGHER you mount the fan, the more cooling you're gonna get.
The reason I put an electric fan in my truck was that my mechanical fan was sitting too low and not performing well enough.
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http://www.alanhorvath.com/54chevy/chevypics/rad_back_newold.jpg[/img]
If you're using a 16-inch fan, I suggest you use
Two Relays -- See Here I also believe in using a
Fusible Link instead of a circuit breaker (and definitely NOT a fuse).