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This post follows a recent post by Tim E on the EarlyCJ5 site describing his conversion of the later-type (late 1967-'69) oil bath air cleaner to accept a paper filter element.  That thread can be seen at V6 Oil Bath To Paper Element Conversion.

Below is a description of my conversion of an early-type (1966-early '67) oil bath air cleaner to a paper element. I actually completed this project awhile back using a slightly different approach than Tim did, but am just now getting around to writing up this post.

I've had the original oil bath air cleaner on my early '67 CJ5 since I bought it in 2009, and until recently, I had no plans to change that. Oil bath air cleaners do a fine job of removing dust from the incoming air, and especially considering that it is original to the jeep, I saw no reason to do anything different.

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Then, about a year ago, the engine was rebuilt and completely repainted. At some point following the engine rebuild, when taking the oil bath off or putting it back on, I apparently accidentally tipped it just enough to drip a little oil onto the top of the intake manifold. After the oil sat there for awhile, it had the effect of peeling off some of my brand new engine paint. To prevent this from happening again, I decided to give this mod a try.

After looking at the air cleaner closely and searching around online for different paper filter options, I was fairly sure I'd figured out a way to make this modification work without altering its original external appearance. However, since I wasn't 100% sure it would work, rather than modifying my original oil bath air cleaner's housing, I looked around for awhile to locate a matching '66-'67 air cleaner, and eventually found one.  Having both a modified and an intact original oil bath air cleaner is what I'd actually prefer anyway, just in case I or someone else in the future ever decides to change it back to the original oil bath type for some reason.

The first task was to use a jigsaw / sabre saw to cut the bottom out of the upper portion of the air cleaner housing. Measuring from the top flange of the housing, I left about 1-1/4" of the metal cylinder in place below it. This metal is fairly thin, so it only took a couple of minutes to make this cut. Once the bottom was cut off, there was a metal screen that was easily removed by hand.  The cut-off metal edge was smoothed using a hand file.  

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The old paint was removed from the lower housing by using various wire wheels on a drill, rather than by blasting. I didn't want to blast it because I was concerned that some of the grit might get caught in between the joints in the metal, get into the cavity, and later find its way into the engine.

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With the upper housing cut open, it was possible to fairly accurately measure the inside surfaces and pick out some different paper filter elements that might work.

On the Wix Filters website, there's an option to sort through all the air filters they make by their outside dimensions. After carefully measuring and then actually experimenting with a few different filters, I finally settled on the Wix 42011. This filter is rated for 90 CFM, and is very common, as it was used for many years in various Chrysler-Dodge-Plymouth vehicles with the slant 225 straight 6 engine, as well as in some V8 applications.

Continuing with the modifications on the upper housing, an angle grinder was used to grind the bottom of the PCV tube more or less flush with inside surface of the housing. This grinding no doubt weakened that joint, so after blasting, I used some JB Weld steel reinforced epoxy to strengthen it.

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I wanted to make sure the PCV system would continue to function normally after the original housing was modified. The way the PCV system on the Dauntless works, in a nutshell, is that filtered air is drawn out from the air cleaner through this tube, down through the crankcase of the engine, then out through the PCV valve and is pulled by vacuum into the intake manifold, where the crankcase fumes are burned off.

One difference between the early type and the later type oil bath air cleaner is that the early type had a cone-shaped bottom flange (see photo of screen removal above), rather than the flat flange the later type had. The solution I ultimately came up with was accordingly a bit different than Tim's.
Rather than mounting a flat circular flange at the bottom of the shortened upper housing as Tim did, I used a stainless steel ring attached inside the upper housing to provide a level surface for the top of the paper filter element to seat against.  This ring also keeps the PCV tube's opening from getting blocked by the top of the paper filter element. Because the ring is mounted up near the top of the inside of the upper housing, the paper filter element used is quite a bit taller in this version.

The ring is 14-gauge stainless steel with a 8-3/4" outside diameter and a 6-1/2" inside diameter (total shipped cost was about $18 through eBay seller Lumberjack1983). When mounted, there is sufficient clearance between the PCV tube's inner opening and the ring for air to pass through the tube. A small notch was also ground into the inside edge of the ring at the tube to ease the flow of air through it. I used Loctite RTV to seal the outside edge of the ring to the upper housing, then used JB Weld epoxy to make "spot welds" around its perimeter to permanently secure it in place. (After the epoxy cured, I filled the areas in between these "spot welds" around the outside of the ring with RTV.)


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To help ensure a good seal between the filter against the cone-shaped surface inside the lower housing, as well as to get the necessary height differential between the lower and upper housings when installed, I picked up a 5" silicone pipe flange seal on Amazon (Silicone Flange Gasket, Ring, Red, Fits Class 150 Flange: Industrial Gaskets: Amazon.com: Industrial & Scientific). I "glued" this silicone ring to the inside surface of the lower housing using the process described here (which seems to have worked well):
What glue do you use to glue silicone rubber to steel

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The exterior of the air cleaner housing was painted with VHT gloss black epoxy spray paint. I've used this particular paint in the past and have consistently had excellent luck with it. It requires no primer, and has a sheen that's very similar to the original air cleaner's black paint. (Note, however, that if using this paint and you decide to apply additional coats after the first hour, you'll probably need to wait quite a bit longer than the 7 days indicated on the can for the epoxy to cure completely first....based on experience, I'd recommend waiting at least 2 or 3 weeks.)

Last, I applied a new air cleaner sticker to match the original, available on eBay from seller jfranzl48.

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The installed modified air cleaner looks identical to the original, and the engine (still) runs just fine with this paper filter setup. I haven't found a need yet to adjust the carb for any differential in air flow there may be between the oil bath and the paper filter element.

And best of all....No More Drips! :)

 

UPDATE 6 / 2017:

TimE on the Early CJ5 forum corresponded with me about this air cleaner conversion project following my initial post above.  During that conversation, he told me about another paper filter he'd found on the Wix website with a higher CFM rating.  I hadn't located this paper element during my own search, as I'd been looking at filters in a different range of dimensions. 

The paper filter I'd used above, the Wix 42011, is rated for 90 CFM.  The filter Tim found was the Wix 46022 (for a 1981-82 Toyota Starlet), which is rated at 170 CFM.   Though it's both shorter and smaller in diameter than the 90 CFM filter, it's also much thicker, which is clearly what allows the significantly higher CFM rating (due to having more paper surface area).  

I decided to try to figure out a way to use the 170 CFM filter instead of the 90 CFM element I'd initially used.  The 170 CFM filter exceeds the specs of the OEM paper element used on the 1970-71 Dauntless engines, which was rated at 155 CFM.  Though at lower RPMs, the 170 CFM filter wouldn't result in much if any improvement over the 90 CFM filter, at higher RPMs it should deliver the needed volume of air with less resistance.  

In comparing a few different brands of the 170 CFM paper element, it turned out that the ACDelco A2980C was a bit more robust than the Wix version, as it incorporates an expanded steel mesh outer surround, while the Wix lacked this feature.  

With one of the ACDelco A2980C filters in hand (about $11 on Amazon), it became clear that with the addition of another stainless steel disc in the lower housing of the oil bath air cleaner, this higher-CFM filter would work with the modifications I'd already made to the upper housing.   In order to modify the lower housing to make it fit, I ordered a 1/8" thick, 9-5/8" OD and 3-17/32" ID stainless steel disc on eBay (from the same seller I bought the first disc through, Lumberjack1983):  

 

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The new lower disc sits on the horizontal ledge just above where the lower housing is stamped "oil level":  

 

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After first removing the silicone pipe flange installed above (which was difficult, as it turned out that the silicone "gluing" had worked very well!) and cleaning everything thoroughly, I epoxyed the disc to this ledge using steel-reinforced JB Weld, and also placed eight epoxy "spot welds" around the disc's perimeter to secure it to the inner steel bowl of the oil bath housing:

 

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Loctite Superflex RTV was used to seal the remaining outer edge of the disc.  It was also applied around the inside, just to ensure that any pinholes that might have existed in the epoxy joint there were sealed:

 

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Here's how the upgraded filter fits on the modified lower and upper housings:

 

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The Dauntless runs great with the revised setup, and the re-modified original housing with the 170 CFM filter still appears to be stock when it's installed:

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Thanks again, Tim!!  :-)

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Nice commitment to the original air filter housing for look, fit and function...Lots of work, but your end result justifies the effort!  Substantial surface area on the pleated paper air filter that you're using.  I like the filter's mesh screen, too.

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HI Moses,

I have some general questions for you re. oil bath air cleaners vs. paper filters.   

I've read that oil baths, while they work well in terms of removing particulate matter from the air, tend to become more restrictive as the air flow through them increases.  However, I've not yet found any conclusive data in terms of a CFM comparison of an oil bath air cleaner vs. a paper filter type.  

The paper filter manufacturers, e.g. Wix, do publish CFM figures for each of the filters the make - but do those figures represent an actual maximum air flow for a given filter, and is that figure generated via a calculation of the filtration / surface area of that paper element?    

When I chose the Wix 42011 filter for this conversion, I selected it based on 1) the fact that it fit well into the modified oil bath housing, and 2) that it is commonly used on similar sized (i.e. 225 c.i. 6-cylinder) motors, as well as some larger V8s.   That particular filter also had the highest CFM rating (90) of the various filters that were within the dimensional diameter and height ranges I needed.

In 1970, Kaiser jeep shifted to a paper filter for the 225 V6.  I checked the data for those particular filters on the Wix website and found that they were shown as being 155 CFM.  My jeep, even with a modified cam that probably somewhat increases the air flow required compared to a stock motor, seems to run quite well on the 90 CFM filter I just installed.  But would it run even better on a  less-restrictive 155 CFM filter like the ones used on the 1970 V6s - or a filter with an even higher CFM figure?  Conversely, could I have used a paper filter with a significantly lower CFM "rating", and still have achieved good results? 

In other words, in selecting a paper filter to replace an oil bath type, is there a "right" way to approximate an air filtration CFM range required by or recommended for a given motor displacement?

Thanks, Moses, and I look forward to hearing your thoughts.  This project, as they all seem to be, is yet another learning experience!

Maury

 

 

 

 

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Maury, see my comments to your questions, highlighted in red below:

On 5/20/2017 at 6:10 AM, snoopy2x said:

HI Moses,

I have some general questions for you re. oil bath air cleaners vs. paper filters.   

I've read that oil baths, while they work well in terms of removing particulate matter from the air, tend to become more restrictive as the air flow through them increases.  However, I've not yet found any conclusive data in terms of a CFM comparison of an oil bath air cleaner vs. a paper filter type.

There are a number of variables.  Years ago, I was responsible for a fleet of light and medium duty trucks.  Many of those now vintage vehicles had oil bath air cleaners.  Worth emphasizing is that all of these engines had relatively low rpm ceilings.  Later, as a 4x4 and light truck journalist, I knew Jack Clifford (Clifford Research and Performance founder).  Jack earned fame around high performance inline six-cylinder engines like the 308 Hudson, 270/302 GMC Jimmy and 235/261 Chevrolet Stovebolt.  He won national drag racing titles that were unbroken for a decade, driving a Hudson coupe.

Jack had a very sensible formula, at least applicable to engine designs of a bygone era, that determined the engine's CFM requirements.  He believed that to achieve a baseline 4000 rpm, an engine's carburetor CFM flow should be equal to the engine's displacement.  As such, your Buick/Jeep 225 V-6 would only require a 225 CFM carburetor to reach 4000 rpm.  To spin faster, of course, the carburetor would need a higher CFM flow.  Even with a "cam", a 300 CFM carburetor would be plenty for these 225 engines, taking the V-6 easily to redline (OEM 4,200 rpm horsepower peak) and sustaining that speed.

The paper filter manufacturers, e.g. Wix, do publish CFM figures for each of the filters the make - but do those figures represent an actual maximum air flow for a given filter, and is that figure generated via a calculation of the filtration / surface area of that paper element?

If you know the actual CFM flow of the paper filter, and if the air intake opening to the filter canister will flow an unrestricted and equal CFM, you can determine whether you've achieved an adequate flow rate.  You would have to perform calculations on the opening to the air cleaner and its volumetric efficiency.   

When I chose the Wix 42011 filter for this conversion, I selected it based on 1) the fact that it fit well into the modified oil bath housing, and 2) that it is commonly used on similar sized (i.e. 225 c.i. 6-cylinder) motors, as well as some larger V8s.   That particular filter also had the highest CFM rating (90) of the various filters that were within the dimensional diameter and height ranges I needed.

Sounds like a sensible choice simply based upon the use of this filter in larger engines, i.e., even V-8s.  Your other concern, as mentioned, would be the air flow into the canister, which should be adequate based upon its original engineering for the 225 V-6.

In 1970, Kaiser jeep shifted to a paper filter for the 225 V6.  I checked the data for those particular filters on the Wix website and found that they were shown as being 155 CFM.  My jeep, even with a modified cam that probably somewhat increases the air flow required compared to a stock motor, seems to run quite well on the 90 CFM filter I just installed.  But would it run even better on a  less-restrictive 155 CFM filter like the ones used on the 1970 V6s - or a filter with an even higher CFM figure?  Conversely, could I have used a paper filter with a significantly lower CFM "rating", and still have achieved good results?

The CFM rating would reflect both the surface area of the filter and its porosity.  Surface area reflects the height and thickness/depth of the filter wall and its pleats.  That the filter used by Jeep was 155 CFM could also mean it was less restrictive, but that is doubtful:  Less restrictive (larger micron size porosity) paper would mean less protection for the engine.  This would be unlikely for an engine operated in dusty conditions. 

Too much porosity (higher micron filtration) is the basis for the taboo against using a gauze filter (like K&N and others) on a diesel engine.  As a point of interest, a dusty, alkaline road in outback Nevada can clog a quality new paper element air filter in a dozen miles.  This makes an oil bath air cleaner seem attractive.  The oil bath air cleaner is more forgiving in this kind of environment. However, I'd like to see data on how much dirt gets past an oil bath filter.  A paper filter, installed properly and sealing correctly, is a clear barrier to dirt.

Another consideration when comparing your current filter to the 1970 Jeep 225 V-6 type would be filter diameter.  This has a direct bearing on the pleated paper surface area.

In other words, in selecting a paper filter to replace an oil bath type, is there a "right" way to approximate an air filtration CFM range required by or recommended for a given motor displacement?

You are limited by 1) the canister height, 2) there is only so much room for the filter's wall thickness and 3) adequate micron filtration is essential.  Accepting that you want sufficient filtration (governed by micron porosity),increased CFM would be limited to filter height and thickness.  When you consider a filter of the right micron filtration, and one that will fit your canister, the thickest filter wall would offer the most pleated paper surface.  Unfolded, the pleated paper's surface area is determined by the depth and width spacing of the pleats.  The CFM rating is the outcome.

You would need to take measurements of the 1970 Jeep V-6 air filter to determine why its CFM rating is higher than the filter you purchased...Compare the pleated paper surface areas and the micron filtration.

Moses

Thanks, Moses, and I look forward to hearing your thoughts.  This project, as they all seem to be, is yet another learning experience!

Maury

 

 

 

 

 

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Maury, in considering the CFM air filter issue further, there seems to be some ambiguity.  The Wix CFM numbers make little sense if you compare them with carburetor CFM requirements.  You did the right thing by comparing applications for the filter you installed.  If a small V-8 can be fed adequate air through this filter matrix, you likely have a good pick.   Application is often the safest way to pick an air filter for a modified air induction system.

If you're still concerned about flow, there are ways to determine whether the filter is flowing enough air.  With a fixed jet carburetor like yours, this is much easier to determine than with an EFI engine that has an O2 sensor.  EFI can, to a reasonable degree, adjust air/fuel ratios to compensate for a slightly clogged or restricted air filter.

In your case with a carburetor and fixed jets, the concern is sufficient air flow and volume over the range of normal engine rpm.  If the filter is too restrictive, the engine will be "choked" and running rich as if the choke were applied.  The degree of restriction and enrichment will depend upon the air flow through the air filter.  If you installed the filter and discovered that the idle mixture became too rich, that would be one indicator of restriction.  You would also need to account for air flow at more demanding, higher engine speeds.

Note: It is normal to lean the idle mixture screws slightly after installing the air filter assembly.  Any filter will enrich the mix a small amount.  When I suggest "too rich", I'm referring to a fully warmed engine that is blubbering at idle and needs a significant idle mixture screw adjustment.

The only real test would be a comparison of tailpipe air/fuel ratio readings with and without the filter installed—or comparing the original oil bath cleaner to your new paper air filter design.  Any filter will enrich the fuel mixture some, but we're concerned about numbers indicating a restricted air flow.  Also, if the filter is restrictive at higher engine speeds, the engine will quite literally run out of air and act as if choked or flooding.  You should be okay if 1) your engine's performance seems normal, 2) the spark plug coloration remains the same as when the oil bath filter was in its original form, and 3) there are no signs of choking or starving for air.  Fuel mileage would be a clue as well.

My mentioning spark plug coloration is important.  With carbureted motorcycle engines and jetting tests, the primary measurement tool has been spark plug porcelain coloration and signs of rich or lean operation.  Lean makes plugs whiter, and too lean can even crack the porcelain.  Richer mixtures look dark brown to black if sooty enough.  With new or cleaned off spark plugs, the aim is to run a fully warmed engine to nearly redline, hold speed there briefly, then shut the engine off abruptly.  Reading the plug(s) tells the tale.

The spark plug readings, if you know what is "normal" for your 225 V-6, should be a reliable test.  Short of driving down the road with an A/F ratio probe and testing equipment hooked up, a DIY Jeep enthusiast/mechanic has few options.  Paying for dyne time to make high speed tests under engine load would be cost prohibitive.

Drive the Jeep and see how it performs.  Under load at higher speeds, make sure there is no loading up or stumbling from lack of air flow.  Beyond that, this filter should provide good engine protection.  Wix is a good product line, and you used OEM applications to back up your filter choice.

Moses 

 

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Note: I've just updated my original post above to show how I improved the initial modification to use a 170 CFM paper filter element, rather than the 90 CFM filter I'd first used.  

Hope this is helpful to those considering converting their oil bath air cleaners to use a paper element.

Maury

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That ought to do it...It looks like a good fit and seal, and sealing out dirt is essential!  Good seal top and bottom?  Lots of filter matrix!

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Yep....both the top and bottom of the 170 CFM filter element seal tight against the two stainless steel discs installed in the OEM oil bath housing.  

Glad to finally have this project done!

Maury

 

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I bet you are!  Is the paper element filter changeover worth the effort?  Did you improve filtration and make servicing easier?  Can you access the filter cartridge readily for inspection and service?

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My goals with this project were:

1) to eliminate the problem of oil dripping onto my intake manifold when removing or installing the oil bath air cleaner (which I learned the hard way was all too easy to do);

2) to resolve this issue without changing the external appearance of the original air cleaner housing, and

3) to accomplish both of the above while still providing an adequate amount of low-resistance flow of filtered air to the engine. 

This mod achieved all three, so I think it was worth the effort involved.   Removing the paper filter element is as simple as taking off the upper air cleaner housing and lifting out the cartridge. 

As with all of the rebuilds and mods I've done on this jeep, I really enjoy the challenge of creating a workable solution to a problem like this!  

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Nice!  I'm understanding of the three goals.  Equally impressed with the ease of changing the cartridge—this is so much better than the balancing act and mess associated with removal of the stock oil bath air cleaner...Great fix!

Moses

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