Thread: How small of an air filter can I use?

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Can anyone give me some advice on air filter sizing? I have 454 with a edelbrock 750 carb. My filter assembly is falling apart and was looking at buying a new one. I wanted to buy a smaller one, but am concerned about starving the carb of air. I am looking at a round element 6"x 2 1/2" unit... What do you think?

IMO, too small. I run at least a 14" X 3" filter on my big block Fords.... I suppose you can get away with a lot less, especially if you aren't fussy about how good of a filter you use.... I use the washable ones and try to have as much air available as possible for the carb to draw in..... The expensive way to check it is have someone with a flow bench check the flow rate of the filter and it's housing, otherwise I'd say bigger is better......

..............to small...................... if paper it may be less then 500 cfms

here is a good web page discussing air flow calculations....
scroll down the page to get the info

http://www.aptfast.com/kn_additional...lter_facts.htm

mike in tucson

Air flow calculations all go out the window on a dusty road. You can't have too big an air filter, but you sure can have one that's too small!

Thx guys, thats good info. Ill look at finding a bigger filter element set up.

If a 350 needs 92.4 sq in of area at 5500 and a 454 is 1.3 times as large as a 350, then 92.4 times 1.3 would mean the 454 requires 120.12 sq in at 5500 rpm's to pass the same volume of air per cubic inch. 14 x 3 would be 131.94 sq in, so it looks like Mr. Severson had it nailed all along.

How about all those engines with dual quads running two smaller filters...? I see them all the time. I would assume that twice the carb is not half the intake flow...

Great thread. I guess the hilborn clone will not be the airfilter of choice for the 460. It only has a 6.5 in. Diameter, 2.4375 in. Tall air filter. This would be way too small by the calculations provided on the link above. Now I'm leaning toward this one
http://store.summitracing.com/largei...m-g3001_cp.jpg
14 inch diameter, 3 inch tall and much, much less expensive!

Originally Posted by Gusaroo

How about all those engines with dual quads running two smaller filters...? I see them all the time. I would assume that twice the carb is not half the intake flow...

It's pretty close to half the flow of a single carb engine when comparing both at full throttle.
That's why stock jetting works well in a multi-carb setup in the initial stages of tuning.
And sometimes it's right on the money.

Dual quads are generally 8 1/2" - 9" apart on center so that means your air filter would be about the same size with height depending on what you want, but 3" is a pretty common height.

Running the math shows about 91" of filter area for each air filter.
182" total and referring to Tech's required air flow figures you're in Fat City with dual quads.

I was trying to keep the motor looking "old school".
I really liked this one, its not too popular, but its only 6 x 2.5


So now I am looking at this one. Its 12 x 8 x 3.
Its pretty common, but I guess it will do

I had my concerns that my 12x2 would really be too small even on my mild 5.0 SB Ford, but it's just about right. If I go to the K&N filter, more then enough.