Air filter flow test

[mmason]

I have often wondered what kind of flow restriction there were with the air filters that I have put on my engine over the years. I decided to give them a flow test on my flow bench.
I used my 950 quick fuel carb. for testing the filters. I can only pull 28" of depression on two of the barrels at a time so I did one primary and one secondary and plugged the other two barrels.
I also covered half of the air filter so I ended up with half a carb and half a filter for testing. All of the bases, tops and filters are K&N except for the 2 inch paper filter witch was a Aflotech filter that I happen to have.
The carb flows 590 cfm at 28" with two barrels and no air filter. The biggest thing I noticed is sometimes the x-stream top works well and sometimes not.


Filter Size             Base             Top             Flow at 28”

2 in paper            Standard       Solid              495
2 in paper            Standard       X-Stream       577

2 in non-oiled      Standard      Solid               575
2 in non-oiled      Standard      X-Stream        585

2 in                       Standard      Solid               560
2 in                       Standard      X-Stream        580

3 in                      Standard       Solid               582
3 in                      1 in drop       Solid               582
3 in                      1 in drop       X-Stream        584
3 in                      Standard       X-Stream        585

4 in                      Standard       Solid               585
4 in                      Standard       X-Stream        589
4 in                      1 in drop       X-Stream        585
4 in                      1 in drop       Solid               585

3½ in non-oiled   Standard      Solid                589
3½ in non-oiled   Standard      X-Stream         588
3½ in non-oiled   1 in drop      X-Stream         586
3½ in non-oiled   1 in drop      Solid                589


Made one change to the 3in drop after retesting

[chris401]

That KnN lid made a big jump with the 2 inch filter. When I was looking at my old air cleaners for the best use. The best looking one I had was an air cleaner from a 58 332 Ranch Wagon. But with the resenator the stock filter size was only good for a 292 at 5500. Gutting the resenator would have helped but it was not far from the inlet being a restriction. If I remember the inlet was only good for a 4500 rpm 390. It was too nice of an air cleaner to start cutting on so I used a dual snorkle from a 1974 Dodge motorhome and ran duct work to the radiator support. I figured the dual inlets are good for a 5500+/- 430 cubic inch.

[jayb]

Great information, Michael, thanks for posting that!  I frequently used those K&D filter tops when hood clearance was a problem, but never really knew if they were effective or not...