Does Size Matter?

[abnovak]

Have a friend who has a 351 with a 14" K&N aircleaner but he likes the smaller 9" chrome air cleaner better. Will he loose performance going to a smaller size?

 

[TheWolf]

If they're both the same type of filter, I don't think there'd be much difference at all. At least not that you could tell.

 

[DarkBuddha]

I doubt he'll notice any loss of performance, but theoretically, it is possible if the smaller air cleaner causes enough restriction to choke the carb. The 14" air cleaner provides for more surface, thus providing less restriction to air to flow to the carb. The formula for the circumference is 2pir so to get the area for each air cleaner, multiply the circumference by the height of the air cleaner. For example:

area for the 14" air cleaner =
2
* 3.14159
* 7" (half of diameter of 14")
* 3" (example air clean height)
= 131.94678" of area

area for the 9" air cleaner =
2
* 3.14159
* 4.5" (half of diameter of 14")
* 3" (example air clean height)
= 84.82293" of area

But, will he notice any performance loss? Probably not since it's doubtful the 9" air cleaner will cause enough restriction. Probably more consequential is that the K&N will outflow a normal paper element (which is a bigger restriction), so if the 9" is a paper element air cleaner, I say stick with the 14" K&N.

Hope this helps.

 

[1969mach1351]

A 351 with a redline of 6000 RPM needs about 101 cubic inches of filter area. Like DarkBuddha said 14"x3" has 131 and the 9"x3" has 84. If he wants a 9" he will have to go with a 9"x4" which is 113 cubic inches.

 

[WRXracer]

ok

ill ask my lady tonight if size matters..

 

[D.Hearne]

If he goes with a K&N 9" diameter filter, then he'll lose nothing. I saw a test where they compared engine performance to filter size using K&N's and even with the tiny 4" filter, nothing really changed much as HP goes. There wasn't 10 HP difference from the smallest to the largest K&N. I believe the test motor was a Chevy 350.

 

[67coupe351w]

Arent air filters rated in CFM? As long as the CFM is as big as your carb there wouldnt be any problem.

 

[Route666]

cubic inches of filter area.

Ahhh cubic inches are volume not area. Did you mean sq inches?

 

[1969mach1351]

oops Thanks for pointing that out Route666.

 

[Route666]

No wukkas!

 

[TireSmoknWindsr]

After reading this thread....my head hurts

 

[65straightsick]

Welcome back to school