K&N Air Filters: Search For The Right Filter By Shape And Dimensions

It was sort of fulfilling a childhood dream to have a musclecar with a dual quad, and Project Track Attack has taken on a whole new life in the past couple of years. We converted it to a dual quad EZ-EFI from FAST, and quickly found out that the dual throttle bodies were a tight fit on the old Weiand aluminum intake manifold. Even with carburetors, we were limited to using the Carter AFB-style because of how close the two plenums are to each other.

Having a dual quad doesn’t seem like it would be an issue when it comes an air cleaner, because there are plenty of dual quad air cleaners on the market. But what we ran into was that the minimum center-to-center measurement was more than the 7.5 inches we have on our intake. When we found one that had a shorter center-to-center minimum, it wasn’t adjustable and we had to cut the base in half and add an inch to it, making a very ill-fitting air cleaner that didn’t seal properly, and it didn’t look very good, either.

A quick trip to the parts store and the only thing we found on the shelf was a 6-inch cotton air filter with a chrome lid. The filter was just 2.5 inches tall; the filters fit but we didn’t really have much choice. After just a few short months of driving, the paper filter elements began to show a bit of dirt, and the filters needed replacing.

It didn’t take very long for the paper filters to change from white to dingy gray.

Adding up the cost of the two air cleaners, and the two replacement filters every couple of months, we found ourselves spending more money than we cared to – especially since this car is driven quite a bit. We went to a few auto parts stores and found the same set up at each store. We needed a better solution.

We’ve used K&N air filters before, but none of the stores carried a filter that would work for our application. If we asked a sales person for assistance, we got the rhetorical, “what car is it for?” – as if that information would be of any help.

There wasn’t a solution at any of the stores we visited, but then it dawned on us that the solution was right at our fingertips – on the K&N Filters web site. So we went back home, and paid another visit to KNfilters.com.

Million Mile Limited Warranty

We prefer the K&N filters over the standard paper elements for a couple of reasons, but the most important of which is that we won’t ever have to replace it. Even though it costs a little bit more for a K&N filter initially, because it’s washable we won’t have to buy another filter – or in this case, two more filters – every few months.

It seems like K&N is setting themselves up by making the filters washable and reusable, but that’s the whole appeal to the K&N air filters. They have a “million-mile limited warranty” on their filters, which means that with occasional cleaning, and reapplying the oil used to trap dirt on their cotton gauze filters, we can expect to use the filter for the life of the vehicle.

What makes the filters reusable is that instead of paper or synthetic materials, K&N uses multiple layers of treated cotton gauze. The natural characteristics of the cotton help provide outstanding filtration and high air flow rates. During comprehensive testing, K&N filters have been proven to increase air flow over a stock, paper filter, and this reduction in air filter restriction allows the engine to breathe easier resulting in increased acceleration and horsepower.

The specially formulated oil is absorbed into the thousands of microscopic cotton threads to create a powerful filtering medium. This helps to trap small dirt particles while still allowing the filter to breathe, and the filtration efficiency is verified using the ISO 5011 test protocol. With occasional cleaning – about every 50,000 miles for highway use –  your K&N air filter will likely outlast your car.

Sizing Up A New K&N Filter

As we mentioned, the K&N filters web site offers a few choices for looking up air filters. Since they offer various types of air filters, including 50-state legal intake kits for many vehicles, a customer can look up a filter specific to their own vehicle. This is where the parts clerk can give you a hand, also, but for a car that has been modified, there’s yet another search feature on the K&N web site that allowed us to find the exact filter that we needed.

Within their search features, K&N allows you to search for a filter by several factors, including make, cross-reference numbers, and by another known factor: by dimensions. We knew that we wanted a round filter, and we also knew what our hood clearance was, and we used that information to search for a filter.

We measured the center-to-center distance on our throttle bodies and had a measurement of 7.5 inches, which means that the maximum size of our filters should be just under 7.5 inches in diameter. We also knew that we had a little more hood clearance over the 2.5 inch filters, so we searched those parameters: round filter; 7- to 7.5-inches in diameter; and 2.5- to 3-inches tall. The search returned several filters to choose from, and by researching the available filters we found one that we liked (E-3403), and it was also used as a replacement filter for a K&N air cleaner assembly (60-1330).

The search feature allows you to search by filter shape, and then to narrow it down to three separate dimensions.

Installing /Cleaning The Air Cleaners

To think that after all of the trips to the various parts stores in town, we had the answer right at our fingertips at the K&N web site. Once we decided on what filters we wanted, we ordered them and began the simple process of installing them. We bought a threaded rod at the local home improvement store, a pair of barrel nuts, and a pair of stainless steel allen-head bolts, all with the same thread pattern matching the standard carburetor air filter mount (1/4-20).

Standard hardware is available, but most gearheads probably already have it in their garage.

We inserted the rod, installed the air cleaner assembly over the rod, and marked the height with a piece of tape. Using the marking as a maximum height, we cut the rod down shorter than the air cleaner, allowing us to install the barrel nut about 1/4 way onto the end.

We used thread-lock on the rod and installed the barrel nut and let it cure, then installed the air cleaner and tightened it down with the allen-head bolt. The thread locker will keep the barrel nut from spinning when you tighten the bolts, and if the assembly is too tall, simply cut it down a little at a time – measure twice, cut once.  Cut it too short and you have to start all over again.

The air cleaner assemblies come with a base gasket for a standard 5-1/8-inch carburetor neck, a chrome base and lid, the 3-inch air filter, and a rubber and solid washer for mounting. We now have a pair of larger filters that are a half-inch taller than the paper filter we had before, and with a K&N cleaning kit we are happy to say that we won’t ever have to replace these filters again.

The new filters are not only larger, but they won't ever need to be replaced.

To clean the filters, K&N recommends using their cleaner kit and special oil application about every 50,000 miles. Apply the cleaner to both sides of the filter, and since the dirt is typically on the outside of the filter element, rinse the filter with low-pressure, cool water from the inside of the filter towards the outside (clean side towards the dirty side) until all traces of the cleaner has been rinsed away.

After rinsing, the filters should dry naturally – never apply air pressure to dry the filter as a concentration of forced air could damage the filter. Once the filter is completely dry, the specially formulated oil can be applied to the outside of the filter for continued protection.

To find a filter for your vehicle, to learn about the million-mile limited warranty, or for cleaning kits and instructions, visit the K&N web site. Now that you know there’s more to check out on the web site, you might just find yourself searching for filters for every vehicle you have, instead of getting frustrated at the parts store.

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About the author

Michael Harding

Michael is a full time Power Automedia writer and automotive enthusiast who doesn’t discriminate. Although Mopar is in his blood, he loves any car that looks great and drives even faster.
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