Stelling/Helling Air Fltr Restriction

[Excaliber]

We've heard about this issue before, thought it was time for a refresh.

The small round typical Stellings and Hellings air cleaners, readily available from places like "Finish Line" are pretty restrictive. So how restrictive are they you might ask?

I've been playing around with my jetting and power valve settings and vent tube modifications and have discovered this:

The Stellings/Hellings are good for about 4 jet size's. I can run a 64 jet WITH the air cleaners or I can run a 68 jet WITHOUT the air cleaners and both setups are equal. 64 jets and NO air cleaners is lean to the point where the car has a severe stumble. 68 jets WITH air cleaners is rich to the point where it occasionally belches "black smoke", but runs pretty darn good. Rich is better than lean after all.

For me, 64 and air clearners for the street. 68's and no air cleaners for the track.

Oh! I'm running dual four barrel Holley's, 600 cfm each, 1200 total. I've disconnected one carb and tried that, run's like a dog, BIG loss of power. Yup, I need both carbs.

High Riser intake, no freakin' way I can run anything taller than a Stelling/Helling, the rear air cleaner already "just touches" the back of the hood when it's closed.

[dcdoug]

Is that with the green foam filter or K&N filters?

[Excaliber]

Green Foam, clean and NOT oiled. Interesting question though, I wonder if KN flows more? I wouldn't want to bet on it just because of the name, but maybe...

Sure wish I had a set of those to test and compare.

[dcdoug]

My understanding is they flow quite a bit more. There are a couple different sizes that fit but are of different heights. I think I have k&n 2570 which is a touch taller, but close enough that I can still run the screens for a pretty original look. There is one K&N that is shorter and very, very close to the foam filter (but would probably flow a bit less).

[Excaliber]

I'm looking into some KN's. HAVE to go with the short ones, I got clearance issues already.

[mr0077]

Ernie, FWIW, in Houston one dyno day I did two back to back runs, one with and one without the paper elements I run (I don't care for the K&Ns), and I got a 7.82 HP and a 8.34 lb-ft difference with and without...no jetting change, but A/F ratio was 12.30 at peak power with the filters on, and 12.25 without. This was on a mild (400 wheel HP) sideoiler with a slight overbore...makes me think it isn't worth the possible damage to the motor to run without a decent filter. Oh, yeah, they were dual 600 CFM carbs also.

[Excaliber]

I don't have a problem running without a filter on the track, I keep the two metal screens in place and just remove the foam. The BIG issue is having to change the jets for optimum performance, thats a PITA.

The 64's with or without the air cleaner element "felt" about the same, power wise. BUT a big ass stumble with the 64's and no element. Clearly to lean.

Maybe I'll try 66's and a filter, I'm getting pretty fast at taking the carbs off and tearing them down.

OH, 6.5 power valve is the ticket for my setup. Which is interesting because the "rule of thumb" for a PV is half of whatever vacuum signal your idle makes. My vacuum signal is 12", half that, 6.0. But I got a BIG cam, 6.5 feels real good.

[dcdoug]

Here are the part numbers with descriptions:

KNN-E-1015 (tallest, flows best, but didn't give me enough clearance with my hood scoop) - this won't fit for sure

KNN-E-2570 (second tallest, just slightly taller than the stock foam filter and fit my car. This will probably fit most cars. I actually put the screen back around this filter so it looks somewhat original)

KNN-E-9181 (shortest, this is probably almost the same height as the stock foam filter, but would flow the least well) - these should fit, but you might try the 2570's first.

[Excaliber]

Looks like,,, KNN-E-9181 for me. My clearance is SO tight. How tight is it? It's SO tight I have removed the gasket between the carb and the air cleaner to get that last 1/16th of an inch into play.

[dcdoug]

Yikes. Go for the 9181. Oh, I think that's the one off a Yugo! I sort of forget, but one of these is off a yugo. Summit has them by the way, but they take a few weeks for them to order them as they are not in stock. Not many Yugos buying K&N air filters...

[Rick Parker]

If you haven't done so, removing the choke towers and contouring the sharp edges and corners with these air filter assemblies would prove very worthwhile, or use an HP body.

[601HP]

I run the Holley 600's on top of a Tunnel Wedge intake. I use the S&H base and top, and K&N filters. The choke horns have been milled off.

Early on I replaced the S&H filter guts with K&N filters. I still wanted to get a taller filter installed, but I had no space available. I looked at how I could lower the S&H base.

a. I Milled off the lowest flange of each S&H base plate.
b. Then drilled two holes in the S&H base plate where the carb float level adjusting screws/nuts are located. Also had to slightly modify the bottom of the K&N filter's rubber base to allow it to sit on the float screws/nuts, because they now protrude through the S&H base plate.
c. After doing the above, the S&H base plate contacted the top of the vacuum secondary cover, and would not sit level. That secondary cover is plastic on my carbs. (I use the quick change covers) So, I slightly ground down the top of each secondary cover with a Dremel tool.

All the modifications are hidden when the pieces are in place.

The S&H base plate rests on the body of the carburetor and I gained about 1/4" - 5/16" reduction in overall height, which allowed me to use a slightly taller K&N filter.

I used the KNN-E-2570. It's 1.875" tall.

David

[Excaliber]

Good tips on getting more clearance David. I considered altering the trans mount to lower the rear of the engine, but I then encountered clearance issues with the headers where they exit the side of the body.

No way I would consider a larger hood scoop, that aint gonna happen!

[dcdoug]

I thought this was sort of funny, given that we are putting these on 7.0L 500hp Cobras:

KNN-E-9181: Fits Mazda 1988-91 with 1.1L and 1.3L. Fits Kia Pride 1989 with 1.1L and 1.3L.

KNN-E-2570: Fits Yugo 1986-1989, Fiat L4 Engine 1.1L.

[Excaliber]

Well I'll be using TWO of them so I'm good for 2.6 liter, or roughly, 3 of the 8 cylinders!

Surprisingly, even with the air filters you really can't "feel" a loss of horse power. I suppose it could be measured via a drag strip run, but on the street it's not really an issue. I can easily overcome the 10" Goodyear sticky slicks in 2nd gear if I get on the throttle to hard. With or without filters, regardless of jet size's. You can only hook up so much power, after that, it may come in handy for top speed accelleration, but it matters little in first or second gear.

[mdross1]

I can say this from experience.It took a call to K&N to get the low down on just how much air my 468ci would need to spin into the 6000rpm range.It also took another hood with a modified Harwood scoop to get it all to fit. A 14" dia by 3" with Extreme top.The difference from the Stellings Hellings was incredible.Well worth the effort.Another plus owning a kit car.

[Excaliber]

mdross, do you recall if you changed jets when you went to a larger filter? That makes alone makes a huge difference on my setup.

While the horse power/accelleration feels about the same, I had a terrible "stumble" through out the rpm range when I mashed the gas until I either removed the filters or changed the jets.

[mdross1]

Actually I believe all I did was change the filter.Had already spent a lot of time dialing in the 850 dbl pump Holley.Since then had Dan Davinci build me a 1000 cfm dbl pump,and almost ready to focus on dailing it in.Been a very busy spring.One thing is for certain will not have to worry about getting enough air to the cylinders.

[Excaliber]

You might not have needed to change jets either. Like I can run 68's AND an air cleaner and the car runs fine, all though under certain conditions it does emit the occasional blast of black smoke. Like if the idle falls to low for to long and it "loads up". Removing the air cleaners, with the 68's results in a slightly improved idle but about the same "feel" for accelleration, power, etc. It then never "loads up".

With 64 jets I HAVE to run the air filters to optomize the fuel/air ratio and get decent performance. Which tells me, that the TWO Stelling/Helling air filters are good for about a 4 jet size difference. A single Stelling/Helling with a single larger carb would no doubt require a different jet size change.

The question really becomes: Can a foam Stellings/Hellings air filter support 600 cfm? It's seems likely that it can, all though that may be nearing it's limit.

If you change TWO carbs by four points each on jet size is that the same as changing ONE carb by eight points? Assuming the single carb equals the same CFM as the two smaller dual carbs.

[mdross1]

When I was trying to dail this carb in reading the plugs,got the motor working great and good plug reads with the Stellings/Hellings and no foam,up to a certain rpm.It was definetly nosing over for the lack of cfm.I took the hood off and started playing around 14x4 K&N.It gave me what I wanted,except for the huge lump now on top of the carb.After agonizing over what to do about a hood,I finally bought another, a Harwood scoop and married the two together.Final result with K&N 14x3 and Extreme cover ,giving the motor all the air it can ingest.This car was built for one reason, to own a Cobra on my terms.It being a kit made the modification very palpable.Looking at the car now, it looks even more knarly.Having the motor work (instant throttle response,and power to valve spring limits)gives me the confidence I need to do what I do.Win or lose it is a pure joy trolling around in this little hot rod.