The Stovebolt Site Forums The Shop Area Engine Shop Air filter CFM question

I’m curious about the data associated with a air filter I just purchased. I am changing over to a paper filter from a oiled mesh type, aka ‘space ship’, using the same canister or housing. Will be using a Carter four barrel. I would think the Carter would be rated around 400 or so CFM’s. The filter data states 25 CFM. This filer is about 4”x8”and round. What if anything does the filter data mean. Heck, my big lawn mower uses more than 25 CFM. THANKS.

4" X 8" is pretty much a lawn mower filter.
What engine do you have the Carter 4 barrel on?

283c.i. I run a performance 350 in a hot rod with a filter not much bigger than that. If one looks at some of the multi carb setup on hot rods, one will see filters not much bigger than a large coffee mug. Granted, there are multiples but only in use when you put your foot into it. Also, as I searched for the correct size, I saw much larger filters only rated to 100CFM.

Since you know the cfm, you must have been here already, http://www.wixfilters.com/lookup/FilterBySize.aspx , if not, it's a really good way to find a filter. You are right to be concerned about the cfm of the filter, it will work for a while, but will get dirty much faster due to the limited area of filter material. You need a much larger cfm ratting if you wish to use it for more then a few months at a time. I see those small 3" or 4" filters all the time at shows and just think to myself how much better the engines would run with a real life sized element! I have seen 454's with dual quad carbs and twin 4" filters, who in the right mind ever thought that was good idea, and on top of that, they look so out of place.

Look at the #42241, it's for a Mack truck, 275 cfm . You may have to modify the top, but it's a much better filter and not much bigger then a 4"x8".

Joe,
You are correct. I used that website to find the filter. Unfortunately I’m driven by size concentrations, as I’m fitting a paper/foam filter to an old school oiled mesh housing. I will most likely go with a K&N when it becomes available (out of stock now).
I emailed Wix the question of why the CFM ratings are so low as compared to carb CFM. The filter you gave for a Mack truck is only 275CFM. Don’t know Mack trucks but surely that suck more than 275CFM. We shall see what Wix has to say. Thanks.

Had a call from Wix this evening. I now am searching for a new filter with a much higher CFM. 52carl had it right. The 25CFM ain’t gonna cut it. The Wix rep suggested a racing filter if nothing else could be found although they don’t filter near as well. He said those coffee mug air filters on big motors just stop the bigger bugs. Thanks

So, at this point why change from the oiled mesh filter? They trap a surprising amount of crud.

You bring up a good point that I had not considered. There is more to a filter than just the square inches of surface area, such as how big the holes in the element are.
A lawn mower is run in an absolutely horrible environment for an engine with all of the dust and grass in the air. That filter needs a very fine element to keep all of that out, but the down side is that the fine element keeps a lot of air out as well, thus the low rating for CFM..
Carl