Re: XE 351c - Hornet scoop and Filters...
I have a tall hornet scoop with a 2" carb spacer. If you want to go UP into the scoop like you mentioned, the max diameter that will fit is 9 inches.
I'm using a 9x3 paper element and there's no difference in HP on or off.......that's going to 5500rpm.
Clearance: I have ~1.5" clearance between the top of the scoop to the top of the filter. My scoop is 1" taller with a 2" carb spacer, which will be the same as you running a low scoop and 1" spacer.
K&N only make a 9x3 or a 9x5 (plus about an extra 1/2" for the base). They also make a custom oval, stretched type shape filter that specifically fills up all of the hole inside the hornet scoop.
If you don't use your 1" carb spacer you can use a standard 14x3" filter, under the bonnet as per normal.You can also add a K&N extreme filter top (14" or 9"), but they're hexy on the $$. You probably wouldn't need one for your setup. Try your new filter on and off (without extreme top).......if there's no change, keep your $$.
Modding a tall scoop: the base that makes it taller is just attached with 4 screws and is easily removed.........instant short one.
What city are you in?
393 Tremec TKO 9"