[Steve C.]

Another interesting conversation regarding the K&N Stub Stack subject....

https://www.speed-talk.com/forum/vie...hp?f=1&t=31458

This from a different but related thread....

The K&N stub stacks really mess up the A/F ratio on the Edelbrock 800 cfm carbs. I spent much of an afternoon on the dyno one day trying to pick up some HP by using a stub stack on a magazine article motor I was working on.
Every time we put the stub stack on there the motor went way lean. We tried to jet up the carb to compensate but then the power was down elsewhere in the powerband.

I ended up calling Curt Hooker at Edelbrock and talking to him. He said that he had seen the same thing during their dyno testing and that they did not recommend the stub stack with their carbs.

I called K&N and they said their products worked great and that they had never heard any negative feedback.

The magazine editor edited all of bad press out of my article when it ran.


.

[Formulajones]

Kind of interesting a few are talking about wanting to try that flat style funnel base from Speedway Motors, and then just sticking a K&N filter lid right on top of that.

I didn't do the math but it seems a 14" filter lid would be less filter area than a basic 14x3" filter. If so that might become another issue on some of the bigger engines making more HP....meaning not enough filter for the air flow requirements.

I have a flat style funnel base on the Nomad, with a 14x4" K&N filter, and then just a regular chrome lid. Plenty of hood clearance on that car, don't need a drop base, and under that is a 2" tall super sucker carb spacer on top of a single plane Weiand intake. It all fits under the stock hood LOL

[Steve C.]

Related to not enough filter for the air flow requirements.

There are formulas available to determine how much air your engine consumes. Some involve the volumetric efficiency and some do not. All include the engines cubic inches and the rpm involved. They can vary some, on mine I've seen 701 to as much as 876 cfm. Although not the actual cubic feet per minute my dyno sheet scfm number was 839 at 6000 rpm.

The K&N website used to have a formula to determine the amount of cfm for the engine. But I believe it has been removed. But a few years ago out of interest I talked with a tech rep at K&N about the air low requirement for my 505cid engine and if the small air cleaner assy I'm using is adequate. According to their formula back then a 505 cubic inch engine at 6000 rpm requires about 745 cfm of air flow. Because of hood clearance issues I'm using a 'small' 9-inch diameter K&N filter assy with the K&N X-Stream filter lid. According to the K&N tech rep both used together would support about 650 cfm. If raced I would just remove the filter.

I mentioned to the K&N rep that there were formulas that differed from his, he was quick to comment that theirs was proprietary to help determine a filter size.


.

[grandam1979]

I run a 14x3 with a filter lid on a 68 Firebird with stock ram air pans over a q jet works great.