Air filters?...What do you guys think? -
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post #1 of 21 Old 02-06-2010, 09:45 AM Thread Starter
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Air filters?...What do you guys think?

Hey guys...I am looking at buying a new airfilter for the CJ. It has the 304 V-8 so I am looking for a good filter...I have always used K&N, But I am looking out of the box and seeing what you all think. I have heard of Spectre...but what do you all use? And what do you suggest for me?

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post #2 of 21 Old 02-06-2010, 01:26 PM
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I was trying to find a previous thread where I had posted an extensive air filter test but couldn't find it. The end result was run from K&N as fast as you can if you actually want to keep dirt out of your engine. I had one on my CJ before I saw these test results, there will never be one on it again.

Baldwin and WIX brands were the best at filtering and airflow amongst all the non-OEM brands. The OEM filters outperformed them all. If there is anyone who wants to keep dirt out of your engine, it's the people who manufactured it.


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post #3 of 21 Old 02-06-2010, 05:10 PM
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I took a friend's K&N filter and held it up to the sun. You could see pin pricks of light coming through it. If light can get through it, I am sure dirt (fine dust) can too.

I agree with Coiz, Wix is my first choice. Baldwin, AC I would run also.
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post #4 of 21 Old 02-06-2010, 06:07 PM
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I had one of those k&n type filters on my weber carb and noticed pin holes in the fitler.
auto parts guy said the pin holes were caused by lack of maintenance.

so I bought a new one and keep it properly cleaned and oiled. I also run one of those foam strip prefilters around the outside of the filter. The prefilter really collects a lot of the dirt/dust, have had no problems with the new filter, will treat it again this spring.

Dirty air is a killer of the engine.

I would us a regular air filter like wix, etc: but have not found one that fits the weber carb air filter frame.
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post #5 of 21 Old 02-06-2010, 08:24 PM
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Amsoil makes some pretty nice filters. But I tend to go with Wix or something similar. But anything is better than a K&N.


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post #6 of 21 Old 02-06-2010, 08:30 PM
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I have gone with K&N, but if I was to do it again I would go with AMSOIL. They make geat filters!

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post #7 of 21 Old 02-06-2010, 10:31 PM
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I prefer stock filters used in stock style enclosed filter housings. These give you a cleaner filter element as well as protecting the element from water, mud etc.... If you don't think your existing filter housing is going to breath enough, you can scour the wrecking yards for one off a performance car such as a Camero, Vet, or any of the BB designs. These use large intakes that will breath fine.
The stock filters will clean the air much better than the K&N. They are cheap to replace and don't require the amount of effort to clean.
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post #8 of 21 Old 02-06-2010, 11:27 PM
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Amsoil vote #3!

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post #9 of 21 Old 02-07-2010, 06:26 AM
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I think the OEM paper ones are the best. I have rebuilt a lot of carbs for folks that wheel and drive the same places I do and without exception everyone with a K+N or other funky oiled filter went back to paper once they saw all the dirt inside their carb and intake that the filter was letting through. Especially when I opened mine with the old paper filter on it and the insides of mine were spotless.

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post #10 of 21 Old 02-07-2010, 08:31 AM
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I agree on the OEM housing and all. Those housings were meant to protect the filter, allow better driveability, and do a good job of filtering/flowing air.

As long as the heat risers and such are still connected, it helps cold weather issues. The surrounding housing protects from the coating of mud/water etc. The element is easy to find - most parts stores will have them if it gets damaged/plugged up. Plus they are usually cheaper to replace than the K/N or even the cleaning kit.

These are not hi-revving, high horse race engines. They don't require that much air to breathe. A good clean paper filter gives plenty of air.


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post #11 of 21 Old 02-07-2010, 09:21 AM
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Hmmm... Thinking "Outside the Box" a little here. It seems to me that 2-stroke engines need more or better air filtration than 4-strokes, as the fuel/air mixture is actually run through the lower end of the crankcase, and thus surrounds the main bearings and rod. So, one would assume that 2-strokes need better filters than 4-strokes. And, what does every major manufacturer of 2-stroke high-performance engines run for air filters? Oiled foam style. So, without getting into brand specifics, I would assume that oiled foam filters do a better job than do paper filters. But, and this is a BIG BUT, with a dirt bike filter, it is assumed that you will clean and re-oil it after every race/day riding. This is just basic dirt bike maintenance, and it's not usually considered a big deal. But, how many of us are going to want to clean and re-oil their filter after every Jeep ride? Probably not many. So, and again, this is all theory and thinking out loud, I guess I would believe that the oiled gauze or foam filters would be the best filters if you were going to do maintenance pretty much every day, but the convenience factor or paper style filters, and our desire not to be cleaning and oiling a filter every single day, might make the paper filter a better filter for real-world situations.

I guess if I were racing my engine and needed the absolute best filtration then I would use oiled foam or gauze and clean it after EVERY run, but for a Jeep that gets wheeled and driven to soccer games and to the beer store and etc., maybe a good paper filter is the way to go. I have an oiled Edelbrock filter currently, and I think it does a pretty good job, but I haven't done any extensive comparison testing, either...

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post #12 of 21 Old 02-07-2010, 12:30 PM
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Tests taken on a $285k machine. 9.8 grams of dust injected per minute at 350CFM.
Quotes from test:
In 60 minutes the AC Delco accumulated 574 grams of dirt and passed only 0.4 grams. After only 24 minutes the K&N accumulated 221 grams but passed 7.0 grams.

Compared to the AC Delco, the K&N "plugged up" nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt.

AC Delco filter ran for 60 minutes before reaching maximum restriction while the AMSOIL and K&N tests only ran for 20 and 24 minutes before reaching max restriction.

Dust loading curves: Most notably the oiled reusable types had an exponential loading response before reaching maximum restriction. These filters had a lower initial restriction, but they became exponentially more restrictive under a constant flow of dirt. This runs counter to the "myth" that oiled media filters actually "work better" as they get dirtier.

As I said before, there will never be another K&N installed on anything I own. In my opinion, a paper element filter with an oiled foam shell gets you the best possible filter medium available.

I am not affiliated with any filter manufacturer or the testing center, just want you guys to have as much unbiased information available to be able make up your own minds. And yes I realize these were taken on diesel filters but the medians are the same for gasoline engines and if anything diesel filters are going to be larger due to the average displacement of a diesel engine and most being turbocharged.


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Last edited by Coiz; 02-07-2010 at 12:42 PM.
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post #13 of 21 Old 02-07-2010, 01:04 PM
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Replacement Air Filter for Weber Carburetors and Other Jeep Parts and Jeep Accessories by 4 Wheel Drive Hardware

do not if you can bring up this site, but does anyone know if you can buy a standard air filter that would fit my weber carb.
the filter looks like the one in the picture.

my auto parts store said the only one they could get this size had to be washed and oiled.

So I bought it and try to keep it well cleaned and oiled.
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post #14 of 21 Old 02-07-2010, 01:09 PM
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I have a holley 390 4bbl. Is is possible to use an OEM type housing on an aftermarket carb. How would it install on an aftermarket carb? Same way?
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post #15 of 21 Old 02-07-2010, 02:15 PM
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2 things about that test that stand out when I read it. By the way here is a better link to read the whole thing.

1. It used the old Amsoil filter known as the TS series, which was dual density (2 layered) oiled foam (DDOF). When the DDOF technology was tested with fine dust particles, it was shown as one of the best technologies at the time (again pre-2004). Also this is why you see DDOF technology used on 2 stroke stuff like hanheld equi,pment (string trimmers & leaf blowers) and many ATVs & dirtbikes, where smaller (fine) dirt particles are of larger concern. Amsoil discontinued the DDOF design in 2005 & replaced with our dry media filters known as the EA series. This new technology was a collaborative effort with Donaldson and is second to none in the industry.

2. If you do some real good research and look into what exactly what is tested in an ISO test you will find that they test COARSE dust & fine dust, this test used COURSE dust! Just because these guys had access to a $285,000 piece of test equipment, it doesn't make them scientists!

There are four things that count in air filtration: flow volume, holding capacity, and filtration particle size at a specific efficiency.
  1. Flow Volume. Some companies focus exclusively on flow volume.
    Three things to know:
    - Flow volume at what pressure drop?
    - What’s your engine’s maximum airflow? Any flow beyond what your engine can use is useless to you. In racing or pulling applications with modified vehicles, a high pressure drop (because of high air flow volume) can often collapse the filter. The engine-damaging results are expensive.
    - Very low pressure drop at very high flow usually means that at least 50% of meaningful wear particles are passing right through into your engine.
  2. Holding capacity. How much particulate will the filter hold before the pressure drop across the filter is measureably reducing your fuel economy or power? In the case of oiled-cotton-gauze filters, how much particulate will the filter hold before it’s passing nearly all the wear particles into your engine? (The classic answer is “not much”.)
  3. Filtration Particle Size. The accepted rule of thumb is that damaging wear particles are those with a size of 5 to 25 microns. Filtering smaller ones is icing on the cake. Claiming filter performance efficiency on particles larger than 20 microns is a warning sign that the filter performance is very poor.
  4. Filtration Efficiency. This is listed as a percentage, which refers to what percent of a certain size of particles are captured by the filter. Beware: in order for either the particle-size or efficiency to have ANY meaning at all, you MUST know both numbers. Any company who quotes one without the other is simply trying to deceive you, and generally implies that their real performance in removing wear particles is average to poor.
Bottom line... What matters is that AMSOIL’s Ea line of nanofiber air filters is 98.7% efficient at 2 microns. According to an SAE research paper, that level of filtration reduces particle-based engine wear to levels so low that it is difficult to detect any wear.
What about certified ISO testing? That’s all legitimately potentially impressive, but “the devil’s in the details”. What’s the particle size at what efficiency percentage? They don’t tell you, so you have to figure it out. That’s pretty tough if you aren’t a trained engineer… and not very convenient for consumers!
So what does that mean? A couple of very important things.
First, “coarse” test dust is exactly that, and it’s not going to tell you much other than that you have a filter. It’s a good test of how well your filter will work in a baja race if you’re eating a lot of dust kicked up in front of you. But is that what you’re doing? If they really wanted to test and demonstrate meaningful performance, they would use “fine” test dust.
Secondly, it means that when they do comparison “side by side” “apples to apples” testing against a much better filter, like a nanofiber media, their filter performance can look very good – even identical. Because as the coarse dust builds up on their coarse filter, the classic “dust cake” forms, enabling the filter to take out much smaller particles than it otherwise could. If they tested it with fine dust, the results would be very different.
AMSOIL doesn’t play games. Ea filters are tested with fine dust by the most respected certified filtration test lab in the nation, and they publish the particle size and efficiency together with flow and capacity data. They tell us everything, nothing hidden. No-one else does that. 15 times the dust holding capacity of oiled gauze filters, at an identical (very low) 0.5 inches of pressure drop. And just try to beat 98.7% at 2 microns. You won't find another filter to do that.

By the way, EAA filters are dry media, quickly cleaned, re-useable, and are also cheaper to use than any other air filter over the life of a vehicle, guranteed for 100,000 miles. This is the technology used in the M1A1 Abrams tank for more than a decade.
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