Now that K&N are officially approved by the coastguard I've got a question, what one to use? I got a couple motors in a boat (Kiekhaefer 482's) that has feet of clearance above the motor. Got me thinking about different air cleaners like the 9" or the 14" or a velocity stack style. Any ideas?

Have a look at this thread, with info provided I wouldn't use one
http://www.offshoreonly.com/forums/g...n-my-shop.html

Big difference between a giant full size one and a little tiny one they sell for the 502 MPI I would not be afraid to use a full size one on top of a motor

I had an 8" by 2" tall on my old small block. It ran identical speeds (GPS) with or without the K&N. Choke horn milled off the Holley carb.

I'm considering another for my current build as I'm limited in verticle space. My buddy talked to one of the race teams at key west and they were running a K&N.

I'm thinking that the more area of filter media is better. Wether you get the area from more diameter or a taller element probably doesn't matter. The critical design feature is a nice radius in the base plate.

Haven't they been used for a long time? My 500efi's have them and they are 2000's so im a bit confused

Been available for at least 10 years

I will add this, I built and dynoed a 462 ci pontiac that made between 570-580 hp day to day, a kn 3x9 took it down to high 530s, low 540's. a 14x4 element paper or kn didnt change it enough to measure. a 3x14 cost 6-9 hp. You want as much area as possible, buy biggest one that will fit if your making over 500 hp, Smitty

That 3x9 K&N only flows about 500 CFM. 3x14 is 800 CFM. 4x14 is 1050CFM.

Really good to know. Thanks all.

bet you won't see any K&N's on K&N challange cars !!!!