Posted for John Huft <aflyer@lazy8.net>:

 K&N has a design guide on their website for filter area required for a
minimal pressure drop.
 
 Area=(displacement X max RPM) / 20,839     I am not sure where they came up
with that constant :o)
 
 This yields a required filter area for a 360 cu. in. engine at 2700 rpm of
46.6 sq. in.
 
 
 John