k&n stub stack

[fishman]

This question is for joe.

I was reading in a cam book and it used your name usuing a k&n stub stack on a 500hp 383 sbc and gaining 20 horse power....is this true and what rpm ranges did you see the increases.....thanks

[Procision-Auto]

I tested one on a chassis dyno and gained 4 HP at the wheels. It was not
only peak power, but rather from about 3500 to 5800 RPM.

The carburetor used was a street/strip 0-4778C, 4150 square bore Holley.

You will find a variance depending on the intake set up and carburetor
design. I wouldn't imagine a race oriented carb is going to see much
of a gain.

[MadBill]

I chassis-dynoed one of the versions that fits over the stock choke horn on an ~ 550 HP 350 with an 850-sized carb with shaft and butterfly streamlining, etc. (actual dry flow 930). The previous test, substituting this carb for a very well-tweaked 750/850 hybrid, gained 19 HP, but showed ~ 13.7:1 AFR at the top end. The stub stack gained no power in this test, but the mixture went considerably leaner, ~ 14.4.
I suspect the stub stack added flow but the lean mixture cancelled it out. Unfortunately, we ran out of time so were not able to fine tune the AFR.

[bigjoe1]

If you are loooking for me (Joe Sherman Racing) I DO NOT see anything good in them at all. When I tested one on my flow bench, the gain in airflow was only 5 CFM, they were claiming up to 40 cfm increase. On the dyno. It made NO differance at all. ZERO. Where did you see an article that I used the stub stak ??Let me tell everybody something else. You know the K & N trick lid with the whole top surface like a big filter. They used to advertize this alot. It ALWAYS LOOSES 5,6 or 7 HP over any other regular chrome lid. Notice they dont advertize these any more??
JOE SHERMAN RACING

[rallye bob]

Let me tell everybody something else. You know the K & N trick lid with the whole top surface like a big filter. They used to advertize this alot. It ALWAYS LOOSES 5,6 or 7 HP over any other regular chrome lid. Notice they dont advertize these any more??
JOE SHERMAN RACING

Very interesting....
Joe can you explain this?

[MadBill]

Just thinking out loud here: Do the filter lids lose power because the carb 'likes' horizontal inlet airflow (in which case maybe we need to re-think the design of dyno air turbine hats) or does the confluence of vertical and horizontal flow cause inlet turbulence? I know such cross-currents can be an issue. In working on the cooling of the late eighties Camaro Z-28s we found that fitting 'chimneys' in the (unused) fog light openings to guide air to the radiator face eliminated the turbulence caused as it intersected the semi-vertical flow from the lower valence and greatly improved cooling performance.

Wonder how a sufficiently large filter lid would perform with the 'regular' filter taped off?

[hopperpwr]

WHILE ON THE TOPIC OF AIR FILTER LIDS HAS ANYONE EVER TESTED THE K&N LID THAT HAS THE "TONGUE" TO BE USED WITH THE 4412,- 2 BBL. ENGINE.........

[andyf]

I did some dyno testing a few years ago for a Popular Hot Rodding article. The K&N stub stack caused the motor to go way lean and cost us quite a bit of power. We couldn't really jet the carb up to compensate since the lean condition was only at WOT.

I called the carb mfg and talked to one of the test engineers there. He said that they had done some dyno testing with the stub stack and that it always caused a lean condition. His feeling was that the stub stack was causing a problem with airflow across the booster but he wasn't too sure. He said just leave the stub stack off and the carb will work better so that is what we did.

[putztastics]

WHILE ON THE TOPIC OF AIR FILTER LIDS HAS ANYONE EVER TESTED THE K&N LID THAT HAS THE "TONGUE" TO BE USED WITH THE 4412,- 2 BBL. ENGINE.........

I have, there was a gain of over 10CHP, quite a bit for a restricted engine. I think we had to jet richer but still had a gain overall.

[SchmidtMotorWorks]

I useed to make some parts similar to the stub stack; one was for a milled choke horn 850 and the other was for 4500.

After several years and about 2,000 parts sold, I still don't really know if they worked or not.

The first ones I made for John Bassets Pro Stock car (must have been about 1989) he claimed huge gains (like 25HP) so I made a molded version. A lot of people tested them and I heard everything from "it's the best thing I ever put on my car" to "my engine melted down, you will be hearing from my lawyer", there are too many variables invloved to know why.

Hartman stole one and duplicated two of my molds for those parts and sold the parts through Comp Cams (I guess they still sell them). I guess they sold a lot more than I did.

[Procision-Auto]

Interesting discussion about the K&N filter top lid. I have never dyno'd
one of them back-to-back, but I'd like to read more about the potential
loss and theories behind the cause of drop in power.

Turbulence seems most logical and fitting. Would the height of the lid
in reference to the venturi opening also play a role in this? I've seen
cases where K&N filter top lids were used in conjunction with a drop base
for hood clearance.

It seemed like a good solution to restore some of the air flow into the
carburetor, as opposed to a cowl hood. Thoughts?

[sledpuller]

what about proflow filter system made specially for the dominator by kn filters?any dyno results?thanks

[Procision-Auto]

Just had a tought for Joe and Bill:

With the top filter cover in use, the engine will likely draw air from
the least path of resistance - the top cover, as opposed to the ring
filter.

Do any of you have the resource to dyno back to back tests covering
the ring filter portion with a few layers of tape? Wrap it well enough such
that air only enters from the top.

I'm baffled as to why the filter lid would lose so much power.

[rallye bob]

Just had a tought for Joe and Bill:

With the top filter cover in use, the engine will likely draw air from
the least path of resistance - the top cover, as opposed to the ring
filter.

Do any of you have the resource to dyno back to back tests covering
the ring filter portion with a few layers of tape? Wrap it well enough such
that air only enters from the top.

I'm baffled as to why the filter lid would lose so much power.

Me also..........

[Barry_R]

I tried one of the filter lids back to back on my recent Engine Masters Challenge entry. I will have to dig out the data - but it picked up the score by 1 or two numbers compared to the normal steel lid. Not a huge gain - but it certainly did not hurt the power at any point in the curve.