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Adler's Antique Autos, Inc.
Author of "Notes from the Corrosion Lab"
801 NY Route 43, Stephentown, NY 12168
(518) 733 - 5749     Email
Preservation and Restoration

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Cars for Sale
Air Cleaners*
by Bob Adler
Question: Is an oil bath air cleaner worth using?

Answer: Sure !

Dust and grit inside an engine wear it out prematurely. The most efficient air cleaner helps an engine stay healthy longer. No one wants gritty stuff scratching up cylinder walls and bearing surfaces.

Early six cylinder air cleaners were oil wetted copper wire mesh. Dirt particles stick to the oil soaked mesh as they pass through the filter. Since it is easy to see through the filter element, considerable dirt can also pass through. 1931 featured a flame arrester which quenched any flames due to engine backfire. 1932 added an intake silencer which is a resonant chamber that damps out the hiss of incoming air. Trucks up through the late 1950's used a small air cleaner as standard equipment that did not have the silencer feature. These stood about three inches tall, while the car units through 1948, with silencer, were twice that height. In 1949 when the car hood was lowered, the air cleaner also was flattened out, but the resonant chamber became much wider. In 1955 when the car hood was further lowered, the six cylinder air cleaner grew a snorkel, putting the filter element and resonant chamber down near the generator with a sheet metal duct attaching it to the carburetor top. Passenger car oil bath air cleaner.

All these mesh filters are an inch or less in thickness, and filter out maybe 50 to 75% of contaminants. It depends on particle size and density and air speed. Better than nothing but far from perfect. Maintenance is easy. If the element is removable (all but the early 1930's) wash it in solvent, let it dry, then re-oil. Many people forget to re-oil the mesh, but oil makes dirt stick. Let excess oil drain before reassembling the filter.

Passenger car oil bath air cleaner.
Passenger car oil bath air cleaner.

Oil bath air cleaners come in various shapes and sizes. Some are advertised as holding one pint of dirt, others two pints. They really are more efficient at trapping dirt than the standard filter. Dirty air enters near the top and is accelerated downward. At the bottom of the filter lies a sticky pool of oil silently waiting. The air makes a quick 180 degree turn just above the oil on its way to the carburetor. Dirt, being denser than air, can't make that quick U turn, so it divebombs into the pool of oil and is permanently removed from the airstream. Air continues through a horsehair like filter which is also oil wetted, then enters the carburetor. All these filter housings have an oil fill line which should be observed when servicing. This provides the proper clearance for the air U turn. Some styles have a short cover which will let water fall directly into the air cleaner. Check hoods with a center seam for water tightness. Always keep these filters upright or YOU get the oil bath. No one makes that mistake twice. Also, if sandblasting a filter housing before painting, consider it may be impossible to remove all residue that migrates into the resonant chamber.

Truck Oil bath air cleaner.
Truck Oil bath air cleaner.

Disposable paper filter elements, which became standard equipment in the early 1960's, are quite efficient at trapping small and large particles in the carburetor air stream. Some sources say these get more efficient in use as the large pores get plugged up, making a finer filter. Throughout the 1960's oil bath air cleaners were advertised as an accessory for heavy duty truck use. Maybe they were just for diehard traditionalists.


  • Chevrolet SPECIFICATIONS 1936 and 1969
  • Chevrolet MASTER PARTS CATALOG 1929-1953

* Originally published in the Vintage Chevrolet Club of America, Inc.'s "Generator & Distributor", Oct. 2002, v41, no. 10, p14.

Bob Adler is owner of Adler's Antique
Autos, Stephentown, New York, and
specializes in GM truck restoration.
He can be reached at 518-733-5749.

Adler's Antique Autos