Stellig & Hellings air cleaner effectiveness

[my427cobra]

So as I go down the road of my final decisions to add a hood scoop (some more tuft testing to do with pics yet to come), I thought about some of the discussion about the Stelling & Hellings air cleaners and their effectiveness.

The concern expressed by some is that the S&H air cleaners are so small that they are quite restrictive. So I wondered about an alternate, especially if a hood scoop will add some nice cool air.

So I went through this analysis:
1) The S & H air cleaners have a surface area of 33.375 sq in each for a total of 66.75 sq ins. But the perforated metal surround only has a 51% effective open area, taking the total back down to 33 sq in . (let’s assume the S&H foam filter flows about the same as a K&N pleated filter)
2) Air cleaner discussions have said a 14 in air cleaner is better ( a 2 in high 14 in air cleaner has 88 sq in). But a 14 in air cleaner won’t work on a 2 x 4bbl set-up.

So how could I increase the total air filter area of my S&H air cleaners?
It has to be through the top. But how?

I could cut screening or perforated metal and fab a top for the S&H base. Sandwich a piece of foam filter material between two screens and attach it to the S&H base. Pricey and a lot of work.

Looking through a Speedway catalog I found these:


Speedway p/n 550-2085 ($19.99 each) and is 8.75 in dia. And it already has the two screens, filter foam and a nice chrome surround.

So I ordered a couple and got started by trimming the chrome surround from the base:


Then I reassembled them and here’s what they look like installed:


So the tops add 56.75 sq in of area each totaling 113.5 sq in but at 51% effective area due to the perforated metal I’m back to 56 sq in.

But adding the Speedway tops to the S&H sides now yields a total of 89 sq in , equal to that of a 14 in air cleaner.

A big improvement over the S&H stock air cleaners.

But do I like the look of them? I think they will have to grow on me.

And I’ll have to make a couple of S&H decal/medallions to install on top.

Now on to the hood scoop fab and installation.
Cheers
Greg

[ACHiPo]

Motortrend did an HP shootout of air cleaner designs. You can sign up for a free subscription to view it. As I recall the "bug eye" type filters were pretty crummy for flow, and the best was a tall horn with a filter on top (need more than a scoop to accommodate that).
https://www.motortrendondemand.com/d...ut/0_f6zyfspf/

[DanEC]

The perforated screen was the main reason I figured the K&N replacement elements would be better from a performance standpoint. Plus the ones I used are about 3/16" taller than stock from memory. That's pretty much all I could fit under a flat hood.

[HTM101]

I used several set ups before I came up with this one. The surface area of this combination is about 170 sq. in. It required lots of cobbling and tweaking, special offset bases, mods to the carb bowl vents, offset air filter mount studs, and necessitated cutting an entirely new opening in my hood. The only off the shelf parts were the K&N filters, and the pair of top filters required surgery to adapt the spun aluminum lids.

I used this K&N formula to determine what I wanted for surface area. I can't center the divisor, 20,839, which is why its offset to the left.

A = CID x RPM
20,839

[DanEC]

Those look nice. At my age I'm not real concerned about wringing as much HP out of the engine as I can - it has plenty for me to putter around the county roads. But I do realize the little S&H air cleaners are restrictive. Running one on a big single 4bbl like some of the SC replicas with a turkey pan must be a real top end limiter unless some mods like yours are made.

[my427cobra]

Nice work HTM 101. You custom made filters look very high tech.

I just wish K&N made their filter in black.

Maybe I could use a K&N filter with a black foam pre-filter to Hide the K&N color.

UNI makes a 30 PPI (course) black foam filter material that maybe I could use on the outside as a pre-filter.

Just thinking.

Cheers
Greg

[my427cobra]

OK. I am now beginning to understand why the Stelling & Hellings air cleaner flow is so questionable.

First, it turns out I was using incorrect info as I calculated the effective area of the S&H filters.

The perforated steel filter sides have only a 28% effective ("open) area, not the51% I had used in my calculation.

And the Speedway air cleaner tops I was using have only a 38% effective ("open") area, not the 51% I had used in my calculations.

Second, the green foam filter is probably a 65 t0 75 PPI (Pores Per Inch) foam which is a "fine" filter foam. Great for particle filtering but not so great for air flow.

So back to the drawing board.

Cheers
Greg

[my427cobra]

Then Argess (John) sent me this Filter Flow Test comparison:


WOW. Does that K&N filter result look great or what!

But wait. What do we know about about those other filters?

Nothing. Because no filter manufacturers actually publish any technical specs about their filters.

How many pleats per inch?

How deep are the pleats?

How thick is the filter material?

What is the filter material?

What is the micron spec of the material?

On the foam filters tested, what is the PPI (Pores Per Inch) spec?

This was a test of brands, not filter material performance.

As apples to oranges as you can get.

Now don't get me wrong, K&N filter do flow the best. But compared to?

As an example. Road & Track magazine did a fiter test of a number of filters compared to K&N on a small sports sedan with 130 rwhp. (yeah I know, not 400 or 500 hp like our cars)

A K&N filter was better than stock by 4%. (almost the margin of error)

But a cheapo K-Mart filter was almost as good at 3% better than the stock filter.

Why were the K&N and K-Mart filters better than the stock filter?

Fewer pleats per inch and thinner more porous filter material. (K&N makes up for porosity by oiling the filter material to trap particles.)

So they flowed better.

So the test chart is interesting but not very helpful.


Cheers
Greg

[my427cobra]

So back to the drawing board and back to McMaster Carr.

So I'm going to try the highest flow perforated metal I can get, 79% effective ("open") area compared to the stock S&H 28% effective area.

Use that perforated metal for the sides and top of the filter.

And I'll use a 30 PPI (Pores Per Inch) "course" 1 inch foam for the filter material and I may oil it although here on the Central Coast dust is not an issue.

This foam will flow substantially better than the stock S&H green foam which is probably 60 to 75 PPI fine foam.

We'll see how it turns out next week.

Cheers
Greg

[CSX3183]

All very interesting. The S&H are correct, for the "CORRECT" look. The K&N look like Kodak carousel slide projector items, frankly, I'd laugh at your engine.

On another note, do any of you REALLY think you are going to be able to tell the difference in performance over the S&H filters, they are restrictive on purpose, to keep the CRAP out of your engine!

What are we talking about 4%, let's get real.

[Jdata]

Hmm..4% on my engine (800) is 32hp.. can I feel it.. yeah.. can I feel 10? No... Can I see the difference? Sure, the time slip.. or side by side race

FWIW, my experiences on the Dyno.. the taller the filter medium the better.

[HTM101]

Originally Posted by CSX3183

All very interesting. The S&H are correct, for the "CORRECT" look. The K&N look like Kodak carousel slide projector items, frankly, I'd laugh at your engine.

I agree! Good comparison. I found myself grinning after reading your post.