Is there a preferred filter area to throttle bore area rule for best air flow?

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,

Some thoughts since now one is biting...

Best air flow is not determined by filter area, but by filter height and flow into the air horn. Obviously it should be double to triple at a minimum like the new style injected cars as far as collecting debris and still able to deliver sufficient air.

Are you using the Holley Sub Stack?
and a open element?
or?
Got a picture with the air cleaner on?

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

good question. I have been working on the same thing with my engine. First it was the air filter housing restricting alot of air flow and now the filter is causing a little restriction at higher rpm's. I am going to try to get a K and N filter and see if it helps. When I remove the filter the restriction goes away completely and the engine runs much better. so there has to be a issue with the filter now. I also want to try some type of cold air intake to build some pressure and force the air though the filter faster. Hope some one has an answer for your question.

Joe

_________________
1964 barracuda 198 slant

I found this site has a formula at the bottom after you go though all the K and N marketing stuff.

it works out ,if you revrse figure it, a 225 slant at 6000 rpm needs at least 80 sqin of filter. The stock old style filters only have 62 sqin. and the k and n filter needs be 65 sqin still to small.


http://www.aptfast.com/kn_additional_st ... _facts.htm

Joe

_________________
1964 barracuda 198 slant

Actually some of it is, because if the CFM passing through the net free area of the filter media is less than the CFM of the carb in the mode it's being chosen for, then you will have a restriction...coupling this with a real world certainty that the filter gets dirty or clogged causing less airflow at any range then you can get a real problem (less air+original jetting number can = rich mix, most engineers will try to test air flow models at about 30% plugged/dirty filter air flow on average)...

Closed element cans with snorkles vs. open element as Ted says are also an inlet restriction.

You can adjust the net free area of the filter by making the element taller or increasing the diameter, using a new pietin. (Narrower passages will also increase the velocity of the air passing through it compared to a wider passage (i.e. if air volume is constant, then air passing through a 2" tall filter will speed up through that restriction when compared to a 3" tall element)

After it's through the filter, the restiction goes to how easily the air flows in the pietin to the throat of a carb...stub stacks provide a good "ramp" that allows for high velocity air to "make the turn" easier into the throat of the carb.

It's interesting to see this at lower velocities than what cars flow at, I attended a demonstration for my apprenticeship and we got to see air flowing through duct, offsets and elbows of various configurations with smoke in the air stream to demonstrate why easy subtle bends flow air better than a tight radius, even with turnvanes and scoops it still wasn't perfect like a nice long radiused arc...

Food for thought,

-D.Idiot

Ted,

I have a cheap Edelbrock 10â€￾ dia. 2“ tall filter when installed gives just 39.2 sq. inches of area.

Sum of area of four throttle bores is 7.7 sq. inches. Plus 30% is about 10 sq inches times a factor of four equales 40 Sq. inches.

[img]http://i294.photobucket.com/albums/mm87/wjajr/Dart%20Engine/100_1271.jpg[/img]

Base of filter housing:

[img]http://i294.photobucket.com/albums/mm87/wjajr/Dart%20Engine/100_1272.jpg[/img]

Not sure what a Holley Sub Stack is. Would this be some sort of device that creates a smooth, or laminar flow along the base of the air cleaner, and into the carburetor?

OK joe,

I’m not a big fan of K&N filters. I don’t think they filter out as much fine stuff as a paper filter is capable of.

A 225 cu inch slant needs 80 sq inch of free filter area cranked to six grand… Look’en like I may need a bit more gross area of filter.


Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,

Take a look at the Holley Sub Stack at Summit or JEG's. Yes, it smooths out the flow. I wouldn't run a 390 four barrel Holley with out it........we always run them at the track when running stock carbs with a choke in place. It makes a big difference in how the carb reacts to tuning.
Too bad the hood sits so low on our cars. You could run an K&N filter top element. That really makes a big difference in flow.

The small 2" side inlet is not very good, causing lots of restriction and odd flow across the air bleeds at various rpm. Can you find a drop base so you can go 3" or more? I think you maybe happier with the flow and tuning especially coupled with a Holley Sub Stack.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Just to add my 2c. I've run with a 14" x 3" filter for years now until I recently tried one like Bill has (9" x 2"). I just got sick and tired of taking off the air cleaner every time I wanted to adjust something on the carb, also I thought the larger air cleaner might have been acting as a big heat reflector directing all that exhaust heat back onto the carb.
Anyhoo, what I found was as soon as the smaller filter started to show signs of dirt on it, which was within a week or so, it greatly affected the engine particularly at higher revs. And when the secondary barrels opened I could really feel them "crashing" in, so I put a vac sec spring in that was 3 steps heavier so they wouldn't crash in.
I couldn't work out why I could suddenly feel the secondarys so much. It was not until I read this in the Holley secondary spring kit then the penny dropped. I put the big air cleaner back on and I could run a much lighter vac sec spring again.
I didn't think my little Slant would need as much air as it does, but there you have it.
Cheers, Jon.

_________________
62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

I think you are probable right about the filtering ability of the K and N. I am going to go out and see if I can find a way to put a larger paper filter on my slant. I think the best way to see if your car needs a bigger air filter is with a vacuum gauge hooked up to the manifold. if it starts pulling a vacuum at high RPMs at WOT then you need a bigger filter or carb. That is what mine is doing now.

Joe

_________________
1964 barracuda 198 slant

This is the only Stub Stack I found at Summit that fits an air cleaner covered 4160. Kind a pricy; ain’t it? Are there other less odiously priced Stub Stacks available for a kindly old piker to purchase?

Are there any easy & inexpensive ways to determine when the secondaries start to open without taking the hood off, and having my wife sit on a fender observing while motoring along a public way? --- Not that that would ever happen even several years after Hell froze over.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,
Maybe used off eBay or get the one from Jeg's, its much cheaper.
K&N 85-0500
Stubstack Holley 390-850cfm 4150/4160 carbs that have had choke horn milled off & do not use air cleaner Will not work with K&N Custom Chrome Racing Air Cleaners
Item# 599-85-0500
Only $29.99

You can try the drop base first and pick one up later.
I would just watch your vacuum gauge. Keep your wife in the car........

Another thought, you could hook up a second vacuum gauge to the secondary diaphragm. Drill/tap for a small brass fitting and hook it up!
At least you will know the opening point. Between the two gauges you should see opening and closing points.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ted:
Another thought, you could hook up a second vacuum gauge to the secondary diaphragm. Drill/tap for a small brass fitting and hook it up!

Oh-boy, I read my other post covering the same topic of secondary activation firstly before opening this post. Where, I spewed some stupid rhetoric based on a diagram in a book, before waltzing out to the garage to look over physical construction of the secondary fast-change housing. There is indeed a flat area that will lend it’s self to inserting a tap of some sort to that low pressure area above the diaphragm.

Palm of hand all ready applied aggressively to center forehead region, and mild cussing is still bubbling up from within.

Sorry for that, I did however entertain my self for a few moments composing that query, while a raging chick party, my wife is hosting, goes on above the Man Cave. The girls are playing “Bunkoâ€￾, and that floor of the house has turned into a “No Man Zoneâ€￾ for the near future… I did get a chance to liberate some miscellaneous eats prepared for the flock before its kick-off.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC