K&N Stubstack

[dalola]

One more..

[GaryUnc]

I had the Edelbrock filter on my Classic Roadster because its the only filter that would fit, until I saw that the foam was deteriorating and getting sucked into the engine. And I found out also they are very prone to carb. fires, when it backfires through the carb.
Just my 2 cents
GaryUnc

[CSX 4027]

Good 2 cents. Probably worth a lot more. I agree

[dalola]

Steve, Gary, etc..
If you read further back into the thread, the guys using the Edelbrock Pro-Fow air cleaners are just using the housing and cage, NOT the urethane foam element. Instead, substitute a piece of polyester filter material(like from a humidifier). Polyester is much more durable and flame resistant than urethane. Of course, it won't filter out the small particles, but also offers virtually no resistance to air flow. I'm trying this as purely experimental. I am under the opinion that most Cobra's are literally choking for air due to limited space. Quick test: Do a couple WOT blasts without your air cleaner. With mine, there was a HUGE difference, and I was using a large, but vary shallow, K&N oval. I'm excited to see what this set-up does. Hope to test drive Thursday.
Dave

[JAM1775]

dalola....Your system looks great! I used the edelbrock pro Flo with the humidifier filter element. I have no more than 1/2 to 3/4" between the top of the Pro Flo and the hood. It did not negatively effect air flow because has no direction to go once entering the sealed air pan but straight down the carb throat . The faster you are moving the more downward pressure. The motor can only USE SO MUCH air but this certainly ensures more than adequate air flow and a colder air inlet. My throttle response on the highway was very noticeably snappier after installing the ram air. Just standing still on a dyno, which was recorded in 88 degree shop temps, my 351w gained 8rwhp and a leaner AF mix closing the hood over the ram air set up as opposed to standing still with no air cleaner sucking in heated engine air with hood OPEN. I must imagine moving at 50-60 mph the gain can be significant perhaps a 15-20 gain. Not enormous but cheap HP just the same. If you need to gain more space(1/4-3/8") between air cleaner and scoop , cut down the air pan bottom rim with a grinder. Even it out with a metal file, place it on a level surface to check it is level and use a carb gasket of course. You can drill holes in the lowered air pan to sit over the carb float adjustment screws. Install rubber grommets in the drilled holes to seal around the carb float screws. When you close the hood the thick foam will fully secure and seal the entire pan. Mine has never shifted and like Dave's lifts right off for carb access when the hood is open.

[dalola]

Thanks, JAM!

Hope to get the foam seal glued and trimmed tonight, then it's test drive time!

Think I can smoke 'em in 5th now???

Dave

[JAM1775]

Hah !! That BB will be smilin wide !

[Andy Barwick]

Dalola,

Having seen the photo's of your filter installation, I anm convinced that you will have considerably reduced any benefit that would be gained by fitting the K/N stub stack.
The stubstack is shaped to allow the air to be pulled in from over the sides of the inlet as well as down the middle, I.E. the large edge radius allows air to be sucked in from an angle up to 180 degrees from the vertical!
This is why, if a filter is installed over a stub stack, there must be sufficient free air space left at the sides and above the stub stack to allow the air to turn into the inlet.

Quote from K&N expert:
"The K&N Stubstack reduces turbulence, improves metering accuracy and increases the airflow by reducing restriction while straightening and speeding up air-flow. The Stubstack was designed to increase the airflow of carburetors by decreasing the restriction AROUND the choke horn. It fits inside the air cleaner housing and slides snugly down over the choke horn"

Also your home made filter will stop nothing apart from rocks.

good luck

Andy

[a427sc]

Coming at this from a slightly different angle here, why not try to set up an air box that seals from under carb to the hood, ala the turkey pan only larger (whole carb inside). You could even make the sides attach to the hood, and seal to the base plate, giving plenty of room to work on the carb. Fuel lines and throttle linkage would go thru the fixed baseplate, sealed off with rubber gromets or such. A check of the K/N spec book could then find a large rectangular type filter like a lot of the FI cars use, maybe two put together, and put it over the carb, sealed to the top sides of the air box at the scoop opening. Much like a blow thru supercharger set-up.

Hey, you've got all winter to play with it.

Don

[JAM1775]

Andy I do remember reading about the substack needing air "around" it as well as"above" it to enhance flow. I agree.

[dalola]

Andy,
Yep, I agree with most of what you say. As I mentioned earlier in the thread, this is an experiment. I believe with the set-up I am trying, the substack will still provide some "straightening" of the air into the carb, as compared to no substack. While this method may not be optimal, I think it will still be beneficial. As to the filter media, the "big chunks" are all I'm concerned with. Rocks, as you so mention, bugs, leaves, etc... The proof will be tonight, when I trim the seal, and hit the street. I will try a few runs with the new set-up, and a couple with open carb., then consult my calibrated a$$ cheeks!

Don,
I've thought about that, too. I wonder if there would be any noticable difference in comparing a set-up with carb enclosed vs. not enclosed. My own totally unsubstanciated opinion is that the air ENTERING the carb plays more of a role in carb temp, as opposed the air surrounding it. I'm sure there would be some benefit to it, just wondering how much.

Hopefully, results posted tonight!
Dave

[dalola]

Well guys, not wasting any time, IT WORKS!!

Trimmed the seal to the hood when I got home from work, made a final check, and hit the country back roads!! After a good warm-up in the driveway, did a couple easy miles, stopped to recheck things. Everything looked good...no movement of the pan...filter in place...time for some fun! Back onto the country road, loping along in 1st gear...nail the throttle...instant tire explosion(same as with old air filter), bounce rev limiter...nail 2nd...instant tire explosion(same as with old air filter), bounce rev limiter...nail 3rd...instant tire explosion(NOT same as old air cleaner), bounce rev limiter...nail 4th...chirping, slight squeeling...very bad feeling at 100mph. Shift into N...deep breathes...blip throttle....thinking to self...WOW, just like NO air cleaner! Found a good pull over spot, rechecked everything...looked good, removed new air pan(no tools, no hardware)...test again with no air cleaner. Same result. With the old K&N, she would generally hook somewhat by 3rd gear. Throttle response is crisper now, and I probably need to tweak the BG a bit for more fuel. Overall, I am super happy with this! My goal of some filtration with no-air-cleaner-type performance is right on!

Some final tid-bits. Total finished weight, with evac tube, 1lb 8oz.
Total height from carb flange to top, 1 7/8 inches.
Total cost, around $80 + a few hours of really cheap labor(me!)

Thanks so much to Ed and JAM for the ideas and help! You guys rule!

Now, just a couple more pix.

P.S. Anyone else who would like to try this, I'd be glad provide more detailed pix and assistance.

Dave

[dalola]

Looking over the windshield(sorry, blurry from hands still shaking after test drive!)

[a427sc]

Looks great. I did a similar seal on my car and found the seal material would blow over in high speed runs. So I used a piece of alum sheet around the outside of the seal, notched and folded under the lower pan and used glue to hold the foam to the outer wall. Looks good, and works!

Don

[dalola]

Don,
What kind of speed are we talking here? I got out at around 110 tonight. Traction concerns, and it was really windy...didn't like the way the car was feeling. Everything was still in place when I stopped to check under the hood.

Just curious...wondering if I will experience something similar at higher speeds(no, hopefully NOT on the street!)

Dave

[Whaler]

Hi Don
Interesting to hear about the foam blowing over on high speed and your fix
I got to thinking about that. Is there not a chance that before your fix there could have been forces from both the high speed wind and the added action of the decent volume generated by engine vacuum?
We all know that the sucking/collapsing force on the inside of your "foam box" (caused by engine vacuum) will increase as the force's available inside area increases. I therefore think you may have seen the effect of two forces working their evil together. Re-inforcing the walls from the inside with aluminum would have worked as well.

Using your idea of an aluminum sheetmetal wall on the inside as a backing for the foam seal, tall enough to work and just shy to maintain the nice upper sealing edge the foam may provide to the hood.
(As you said you glued the foam to the outside face)

We know they provide wire ribbing in hoses so they cannot collapse under suction or vacuum.

I enjoy this particular topic and the 3 page read because I have yet to buy my air cleaner for my ride.

Tim

[a427sc]

There are a couple of differences in my set-up than yours, if I look closely at the pictures you put up. My seal was to the bottom of the hood, surrounding the scoop opening completely,with only a very small (>1" total) opening at the rear to accomodate a pair of crankcase vents. Yours appears to seal to the inside of the scoop, thus the missing front side. I guess my carb inlet is lower than yours ref hood. The blow over was caused by two events. I was going in excess of 155 mph at Watkins Glen with a scoop that is both higher and wider than the standard Cobra unit, thus introducing more air volume and pressure with no place to bleed off. There was also very high under hood temperatures as it was 90+ during the middle of the day and the run groups were 30 minutes long. The heat softened the foam and let it blow over (to the outside as it was). The wall is outside the foam, and glue was on the outside of the foam/inside the wall. Sorry for the confusion. Interesting idea the combination of high underhood pressure and carb vaccum pulling it in, but not in my case. Anyway, I use a 14" dropped base and a 4" element which protruded thru the hood, thus the high/wide scoop.

I would be concerned about the instabiity at 110 too. Aero has been addressed numerous times here before. My ERA runs in a decided nose down configuration with no spoilers, and a single racing screen. Was rock solid on a smooth race track well over 150 (maybe even as high as 165). On the street on a windy night is a different story.

Don

[JAM1775]

I have been running my ram air since 11/99. Using the Moroso foam at 3-4 inches thick with a tight seal it should not move. But now you guys have me thinking about highway effects. Could it be the carb pull is somewhat offset by the rammed air ? I will keep an eye on mine and surely use an aluminum reinforcement on both inner and outer edges. Thanks !
Dalola....I had the same reaction as you when I put my ram air pan on ! The snappier throttle on a roll was my first discovery. If you fatten jets, I found just 1-2 up in the rear did the trick for me. Holley go +1.. BG go +2. MAYBE. That left me with a ten point spread between front/rear which BG advised was fine. It maintained the primary, around town AF mixture, but provided just a bit more fuel when I laid into it and began gaining momentum. One jet in rear may do it. BUT our motors may have all the fuel they need if jetted right. It is unburned fuel we may lose at high rpm caused by restrictive air flow that the motor now may be able to burn . I am no expert but I think the air moves through the intake cooler and faster for a more "efficient" burn. Therefore you may need no jetting or just one jet in the rear. My biggest gain was in the 5000-6000 range in 3rd/4th. I could hear and see the difference in the tach. I don't even look during 1st/2nd...too much going on.

[dalola]

Don,
I would imagine the wind forces of 155 compared to 110 are quite substancial, so I understand your course of action. I eventually may have to adopt something similar, we'll see. You are correct in the fact that my seal is to the inside of the scoop. It just so happened that matched up with the size of the air pan, and the contour of the scoop may actually help hold the seal in. The front lip of the pan is about 1/4" from the lower opening of the scoop, thus no seal needed there. This season is, for the most part, over here in Ohio. Next summer, we'll see how it holds up in more taxing situations. So far, I'm very pleased.

Best of luck to you if you decide to build the "big box"! I'd love to see it if you do. Perhaps you could post some pix back here?

Regards,
Dave

[JAM1775]

155 !!! Oh my Gah !