9" Air Filter Drop Base - How Much Interest?

[Bill Wallace]

I made my own out of an old piece of 1/8" aluminum that was a bottom cover protector from a dirt bike.

I made a form by using a jig saw to cut a circular hole in a piece of 1 1/2" by 10" board, then used a router with a bullnose bit to route the shape of a flange in the wood. Then I cut a hole in the aluminum that was about an inch smaller in diameter than the hole in the wood. I clamped the outside edge of the aluminum to the outer edge of the wood, then heated the aluminum around the air horn flange with a plumbers "map" (not propane) torch, and slowly beat the aluminum into the shape of the flange routed into the wood. I used the back of a hatchet to hit the aluminum to ensure I had a convex shape and avoid creasing or flattening the aluminum. I used a spray bottle to water down the wood so it would catch on fire.

Then, I used a belt sander to flatten the bottom of the air horn in the aluminum to ensure a tight fit around the top of carb. It looks pretty crude but it works fine.

I use a K&N X top filter and had to trim about 1/8" off the passenger side of the opening through the hood to allow the hood to close over the filter.

[YerDugliness]

I'm just curious, guys, now that thread drift has taken the discussion to CFM for various filters.


Seeing as K&N makes 9" diameter filters in various thicknesses, would you think that the greater CFM would come from the thicker filters (2") or the thinner filters (1"). There is also a 1.5" to muddy up the waters even more.

It seems to me that the thicker filter, the 2", would have deeper pleats in the filter material, yielding greater filter area. That seems to me to provide an advantage in CFM...anyone have any ideas? For right now it's just one old retired schoolteacher type postulating.....or is that hypothesizing.....or......well, anyway.....

Cheers from Dugly

[FUNFER2]

Hey Douggie !

Sorry, I didn't mean to change the thread.

We run 2" K & N on the sprint car with no cfm depletion problems but, it's always at top rpm when the injectors (or carb in this case) are fully open and sucking in a lot of air, not at idle or street cruising. I'm sure with a clean filter, you wouldn't have an issue. That would be a nice comparison test on the dyno.

[YerDugliness]

Originally Posted by FUNFER2

Hey Douggie !

Hi, Kev! Good to hear from you again, and good to hear that the track car is still kickin' ass!

If your sprint car can run at high RPM's with a 2" K&N, I'm sure my 302 won't have any problems with one....no need to hang on to that 2 3/4" and I can sure use the clearance when I change out the intake manifold!

Cheers from Dugly

[FUNFER2]

Ya, it's been too long buddy. We need to take a new tour to Hurricane ! lol
I don't think that stock mouse motor would have enough suction to suck up a fly !

You need a monster motor like my 527 side oiler. Ya know, needing a tornado to suck in enough air.

Come up sometine and we'll run a test on the dyno.

[Bernica]

Agreed. I am a stubborn SOB with a fixation issue once I have a problem to work on. Drives the wifey crazy! I will figure this one out!

[FUNFER2]

Me too buddy. I usually throw the damn thing across them room. Then everybody take a break, and won't come back until they hear me working again, then it's safe. My wife just said, yeah,... right !

[YerDugliness]

Originally Posted by Bernica

Agreed. I am a stubborn SOB with a fixation issue once I have a problem to work on. Drives the wifey crazy! I will figure this one out!

Let's see if I understand this one.....the K&N 9" hits the inside of the hood scoop by 1/4" on both sides?

I looked at your photo....is that a liner on the underside of the hood? If so, could that be trimmed without having to cut on the actual scoop, itself?

If the 9" is just out of the question without trimming the scoop, would you be interested in retaining the current Stellings 8" air cleaner with an 8" diameter K&N filter element? Here's an 8" X 2 1/2" high one, that might solve the problem (but I hate to see you stuck with that fantastic K&N X-Stream FilterCharger assembly .......no 8" X-Stream filter top, though):

http://www.knfilters.com/search/prod...px?Prod=E-4720

And here's a taller one (2.438") in an 8" OD:

http://www.knfilters.com/search/prod...px?Prod=E-1015

If using the current air cleaner and the 8" K&N is out of the question, well, keep in mind that the original CSX's had a hood scoop attached to the hood with rivets.....it IS an original look and if you have to have surgery on your hood, it's an option.

Lowering the engine that far is going to be a bit of a challenge......

Keep on keepin' on!

Cheers from Dugly

[Bernica]

Thanks Dugly!

Yes, my CSX has a "riveted" hood scoop. Actually, it is held on with tiny stainless button-head allen bolts. So, if I REALLY have to, I can remove it and enlarge the opening. Unless I dare try it from below with a router or something similar

No, I'm not lowering the engine. Funny.

My metal spinner friend is turning the flat base plate today. We'll see how it works out and I'll post a pic.

Cheers!

Michael

[jdean]

This new Airaid 3" filter is tapered a bit. It solved my clearance problem. With a dropped base it would fit a lot of cars.

[FUNFER2]

That's interesting. So you have a width problem in your scoop, how much extra space do you have ?

My problem is towards the front, of the scoop, not width.

[Tim Brewer]

I don't see any way possible a drop base would reduce any ammount of CFM, providing the top of the filter remains at the same height which naturally increases the height of the filter which in turn should increase CFM.

[FUNFER2]

You'll still have some of the filter below the carb seat, thus reducing the cfm.
If you have a tall filter, then you wouldn't need the drop base. Like I mentioned, we tested a lot of filter elements, oval, round, stacked filters ect, and the drop base.

[jdean]

Well the Airaid is definitely NOT a solution if you want to keep a turkey pan. It is a 14" base and tapers to about 10" at the top. The main point of this one is it will move a lot of air and not serve as a restriction to breathing on a fairly healthy engine.

[YerDugliness]

Interesting data, jdean!

I wonder if you could tell us what the other numbers indicate--is the % figure the filtration rate (my guess), no idea what the number after the % sign is, perhaps square inches of filter area (again, my guess)?

I drove a '65 GTO for a while, opened up the hood scoop and used an aftermarket air filter that used foam at the top of the "funnel", or venturi, shaped base. I was not happy with the filtration and feared that a backfire would start a fire in the engine compartment. I don't know that I felt any positive difference in the performance of the car, but it didn't seem any slower, either.

One thing is sure, with my stock-block 302/5.0 HO, I won't need to worry about having enough airlfow with a 9" X 2" or 2 1/4" K&N. That relieves my concern about going to a shorter filter!

I'd bet there is HP to be found with experimentation regarding the structures inside the air cleaner assembly, such as the "vanes" you mentioned in the Airaid. I could see a "funnel" shaped insert (for lack of a better term) inside the air cleaner that would force the air to make the 90* turn into the carb's venturis a bit less turbulent....much like the swirl patterns on some intake valves increase the flow rate.

Interesting.....thanks!

Cheers from Dugly

[jdean]

Dugly,

Here is where the data came from....great article on filters.

http://www.reklessracing.net/forums/...p?showtopic=18

[YerDugliness]

Thanks--the "swirl coefficient" would, I assume, reflect the buffeting effect from the air stream having to make the transition from horizontal to vertical. If that is so, I would assume that the "X-Stream" filter tops we have been discussing here, which in effect have filtration material on the top of the air cleaner, would offer reduced buffeting since they would already be presenting airflow in a downward/vertical direction.

http://www.knfilters.com/search/prod...x?Prod=66-1101

While not exactly the same as I used on my GTO, here's a Mr. Gasket product that does look similar:

http://mr-gasket.com/ProductDetails....txtSearch=2085

I see the "glass-fiber" filters flowed best, but obviously they would be a poor choice for a high-mileage street engine. NASCAR engines are rebuilt after each race, so if any fiberglass should find its way into the cylinders, it would not present that much of a problem.

Great article, thanks!

Cheers from Dugly

[Bernica]

OK guys, here's where I am with the project.
I am including "before" and "after" pics. I had a metal spinner do the tooling for a 9" flat base, out of .050" aluminum material. The pics are my prototype, so it's a little rough.
As you can see, the base is FLAT with a turned-up outside edge and 5-1/8" center hole. The next challenge was the outside edges hitting the float adjusters. I made a small round notch on each side and it dropped right on!!
It still sits on the carb lip, so it doesn't touch any parts of the carb. I don't think the air filter is compromised at all by the small notches.
I believe that this is the absolute lowest baseplate available for a 4150 carb!!
I have now been able to triple the filter area previously being used (with an x-treme top), without cutting into the hood for side clearance. It all fits under the bottom of the hood profile. If I clearance my hood scoop opening a mere 1/2" on the sides, I could go even taller!!

The .050" material could be anodized as well.

So, how much interest out there?? I have the tooling done and can pop some out if there is enough demand. I still have to figure out my costs, but I'm not trying to make a killing. I'm just glad I solved my problem!!

Any feedback, suggestions etc are most welcome.

Thanks!

Michael

[Bernica]

Sorry to follow up on my own post, but maxxed out on pics.
Here is a pic of the plate sitting on the carb...

[YerDugliness]

Looks good, Michael! I'm curious, in pic #5, the item on the left is your new flat plate, the center item is the old Stellings base, and the item on the right is the K&N base, right (on second thought I see the old Stellings in the background, what is the center item in photo #5)? The difference between my old "aftermarket" base plate and the K&N looks very much like the difference between the center and right items in pic #5.

Looks like pic #3 shows a bit greater height, how much clearance do you have when you close your hood? I went to WalMart and got some clay from the toy department, put wax paper on the top of the air cleaner, then put clay "globs" on the various points around the air cleaner and at the center of the air cleaner, then wax paper over everything and just closed the hood, measured how thick the globs were after they were squashed down by the hood. I have between 1/8" and 1/4".

Would you mind posting a photo of the flat base, showing the notches you made to clearance the float adjusters (I assume your DP has center-hung floats, right?)? I know that a flat base will not work on my Edelbrock carb, but as I have said I foresee a small (600-650 CFM) Holley DP with center-hung floats in the future for my 5.0 HO engine. I'm just curious if the "notches" you put in the base might provide an entry point for unfiltered air.

[EDIT--never mind, I can see clearly in pic #4, and I didn't even see the second posting at all....clearly just a small notch on the outer edge of the base plate, no unfiltered entry at all, GREAT!]

I think your setup looks GREAT! When I get ready to change out my intake manifold, I plan on downsizing the round filter to a 2" high model, that will give me the .75 inches I need without lowering the engine/transmission. If I want more, then I need to deal with convertible motor mounts and transmission mount and the resulting effect on the headers, not sure that would be worth it. The X-Stream filter top is a great idea (I wonder if there's any information regarding how much additional air it will flow), not to mention that the air entering the scoop will be "rammed" right down onto the filter top. I don't run a turkey pan, but that doesn't mean I don't want to!!

Cheers on a great solution, Michael!

Oh, yeah....any idea of price? I wouldn't need anodized, but if that were the way they were offered I would still be interested. I might also be interested in one without the reliefs for the float-adjusters, might be able to modify it to fit my Edelbrock and get an additional 1/4" of clearance (that's the "height" of the flange on the bottom of my current base plate)--that would allow me to run the 9" X 2 1/4" K&N filter.

Dugly