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I've been able to track down the last component (the tray) I need to run my oil bath air cleaner. I've gone back and forth on whether to pursue a paper filter (which has been surprisingly hard to find using the dimensions from the original element), but I would like to try to use the oil bath as intended.

The owners manual for my 23rd series just talks about using SAE 50 engine oil in the summer, and I've read in the '51 owner's manual that the mesh in the air cleaner should be oiled as well.

My question/concern pertains to the mesh, i.e. filter media in the air cleaner element. The coarse horse hair is really very brittle now, and I'm guessing that a lot of the material has disappeared over the years. My questions are:

a. how much filter media should be in the element, i.e. should it come to the top of the element (mine sits about an inch below the top), and;

b. given the brittle quality of the horse hair, should I be replacing this media with something like a copper/stainless steel mesh, hog hair, etc. inside the housing?

I'm guessing some "surgery" on the element will be necessary if changing the filter media? Any suggestions/advice are welcome. Thanks in advance, everyone!

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I believe it has been reported the original material used in the early air filters was not animal such as horsehair etc but rather a plant fiber, specifically a coarse fiber from the Kapok tree. This is a different material from the more easily found fine Kapok fleece fiber once commonly used as insulating material in some sleeping bags and outerwear.

The material should be almost flush with the bottom openings and if the fiber has dried and deteriorated enough to lose a significant volume then I would be concerned it would also be dry enough to break off and be sucked into the engine if the filter is put back in service. IMO, it should be replaced.

It may be difficult to find the proper kapok fiber but I know others have replaced the material with easily found copper mesh which comes in rolls, and in some cases even coarse Brillo pads from the supermarket. Since the filter will not come apart without destroying the crimped over connections it will not be an easy job and no idea on the specific amount of mesh required. I would probably try to cut the mesh into lengths and work the pieces in the slots laying it as evenly as possible to end up with an almost full container -- but also taking care not to pack it in so tightly air flow is restricted. When it is inverted gravity and maybe a bit of persuasion should make the mesh drop down level with the openings. A dip in oil to wet the mesh and then blowing or shaking off the excess would probably be a good pretreatment before going back in the filter where the oil splash from the reservoir will keep the bottom side moist enough to trap dust particles.

Thanks very much, Howard. I wonder about just taking cut-to-fit home air conditioning material and just layering it? Would just worry if that'd result in too much restriction?

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Personally I would leave it alone as long as it’s clean because it’s the oil that does the actual work of filtering.

I agree with Don,
The medium is simply there for the oil to wick up and increase its surface area to enhance the amount of oil for the particles in the air to stick to and not enter the carburetor. It was pointed out in this forum that during the ash output of Mt St Helens in the 80's, cars with oil bath air cleaners were not affected by the caustic abrasive in the atmosphere. Add to that our cars have road draught that puts smoke in the air that fouls paper air cleaners faster than a new car.
Bob J.

A soak in oil may make the fiber rejuvenate to some extent but my concern with leaving it alone is if the fiber is as dry as described -- or at least dry enough that sufficient fiber has fallen out to have lost noticeable volume -- will it be deteriorated and dry to the point of fibers breaking off and entering the engine to become an abrasive or when burned, a deposit somewhere.

So here's what I'm going to try... cleaned out the element in gas, was SUPER dirty. Bought some MERV 1 cut-to-fit filter material, cut it up, and fed it through the webbing so that all the original media is on the bottom of the filter. It still doesn't come up to the top, which I figure is fine because I'm guessing the filter media shouldn't be compacted, but it should prevent little strands of the original fiber from getting sucked into the carb.

Only fear is that it's too restrictive, but it'll be easy enough to remove the MERV-1 filter material if it's bad.

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I seem to remember metallic mesh being used in some oil bath air cleaners . . . a lot like a large scouring pad. I went looking on the web and found 6, 3-inch pads for less than $3 . . . stainless steel no less. If the 3M material degrades, SS scouring pads might be a ‘bullet proof’ option. Your right about keeping an eye on mixture, because if the media is too restrictive the mixture will surely enrich. If you suspect enrichment, it will be more severe at higher air flows, but will affect idle as well. A clue would be a different idle mixture adjustment is needed with and without the filter installed. Both the WDO and the WGD carburetors are vented to the engine compartment, and as such would be sensitive to a change in inlet restriction. Remove a spark plug after a bit of exercise to double check. Who knows, with the amount of alcohol in the fuel a bit of extra restriction might be welcomed.
dp