The Glovebox Manual

Making your way around the Stovebolt Forums. Article taken from our March 2009 News page.


The ole oil bath air cleaner... fine technology, back in the day. And still works fine.... as long as you don't mind the gooey mess and junk that collects in it over time. Ah yes, there's a reason time and technology left the oil bath behind ... Nostalgia ain't what it used to be so if you want to leave the mess behind but keep the look, here's a 21st Century way to accomplish an ...

Oil Bath Air Cleaner Upgrade
By Marc "Nhluvstruck" Gagnon
1951 Chevy 3100 5-window
Bolter #36298
New Hampshire
More discussion about this topic in the Engine Shop Forum April 2016

<<< click on the images for a larger view >>>
To view them all in a slideshow on Photobucket, click here

Stock appearance but upgrade performance

There have been many posts about upgrading the oil bath air cleaner, but I have never been able to find detail descriptions or photos to document it.

My goal was to retain a completely stock-appearing air cleaner on the outside while upgrading the function to a low-maintenance / higher performance modern standard inside. Here’s how I did it.


Variety of styles and sizes

I understand that there are several different sizes and styles to these old oil bath air cleaners.

Here is what I started with. I believe it is referred to as a 1-Qt. If you have a different size or style you may be able to adapt this method.

The “bowl” piece on the right in this photo needs no modifications – just clean, blast, paint and set aside for now. The “cover” piece on the left (shown upside down) must be cut open and cleaned out of the old filter fiber.


Understanding the airflow

At this point, it is important to understand how air flows through this unit. Air enters the annular space between the cover and the bowl, travels downward to the oil surface at the level of the “baffle plate” (the ring with the 6 oval slots at the bottom), makes a u-turn in the space between the baffle and the cover, and goes straight up through the filter media.  It then enters the open space above the filter media, makes another u-turn, and goes down the center tube in the bowl to the throttle body. We need to deal with this S-shaped path when thinking about adapting a standard round filter element to this housing.


Cutting into the unit

The first step is to cut off the baffle plate -- this will be discarded so just cut through the sections between the ovals with a dremel cut-off wheel or good aviation snips and remove the outer ring.  Note that you will leave the inner mounting ring attached for now. You can now see what this looks like inside:

The coarse fiber media in mine was decomposing and shedding pieces everywhere -- it had to go! 


At  first, I removed one “spoke” and dug out a bit of the fiber to get a first look at the inside upper area.


You can see there is a similar “open spoke” ring at the top that retains the fiber mat in place. This upper ring also serves to mount the inner support tube that secures the cover to the bowl at the correct location and therefore must be retained to maintain the original look.

I then proceeded to cut out the remaining lower spokes and clean out the remaining fiber.



More cutting

Next step is to remove the remaining inner mounting rings from the baffle and lower spoke attachment.

I did this by slicing the rings with the cutoff  wheel and then prying the remnants from under the rolled over lip  on the center tube, which you need to avoid distorting. (Note: you can see where I nicked the lip with the cut-off wheel – you should be more careful…)





Here’s the completed cover modifications ready for the next step.




Measurements, calculations and sketches

Now that I could see what space there was to work with, I made numerous measurements and sketches and went researching. 

Given the air flow pattern needed and the dimensional constraints, finding an exact filter match is challenging.

  • The ring filter must have an OD less than ~7 inches to allow air to flow up between the cover and outside of the filter.
  • The filter must have an ID large enough (greater than ~4 inches) to allow air going through the filter to turn up and into the upper cover chamber around the support ring.
  • The height of the filter must allow the cover to sit at the proper height while sealing tightly between the bowl and cover.
  • And lastly, you need to seal the outer area of the upper support ring so that unfiltered incoming air doesn’t bypass the air filter. 

More research to find a match

Luckily, the K&N site comes to the rescue with an incredible dimension-based search function. Inputting my constraints yielded exactly ONE suitable option: the E-4583.

Using the listed exact dimensions, I made a mock-up to confirm the fit.

Realizing I needed a bit more clearance around the cover. I shaved the lip with some snips and rolled the edge over with a body hammer/dolly.

Looks like this filter will work just right – time to go find one!

Drilling down through the part numbers in the K&N site, you’ll find cross references by application and manufacturer. This is for a Kohler or John Deere (among others) tractor. I spotted a Lowe’s reference #59583, went to their web site and searched their inventory. A nearby store showed one in stock. 

Rushing down there I managed to locate this in the discontinued clearance area:

Way cheaper than a $35 K&N and just right for experimentation.

Because of the tapers in the bowl bottom and the top spoke ring, measuring the exact height needed was near-impossible. So I estimated low to be sure the filter wouldn’t raise the cover off the mounting flange and not look right.


Testing the theory

The first test fit showed that the filter moved around within the closed assembly. Knowing that I had to also seal the top spoke ring, I killed two birds with one stone: I cut a foam ring ~1” height to fill the upper ring space and secure the filter.


This green foam (see the post script below) is an open cell type as is used on many small engine air filters. With this ring in place, the filter element stays in place. And although it doesn’t completely block the outer space between the cover and filter, it does fill it with a filter barrier, while also allowing a bit greater air flow to the engine. Here is a picture of an optional upper donut to block the outter airflow path.:



With the pieces all painted (and new decal applied) this looks as good as new and should perform better than new! Here is the "before" picture!


Post Script 

Stocking up

This filter is going in my stock 216, so I don’t believe air flow will be an issue.  As there may be some concern over the continued availability of this filter, I plan to go out to as many Lowe’s I can find, and gather any inventory I can!  

For a higher performance Stovebolt, you may want to go straight to K&N. (I have always used them in my sports cars and feel they are worth the price.) Additionally further alterations to the cover like drilling out breathing holes in the center tubes and outer shell below the bowl level so as to not be visible, could certainly provide air flow gains.  Until I test this under driving conditions, I elected not to do that for now.

Short of that, another approach occurred to me as I completed this project. The green foam I have is in 3-inch thick slabs.  I cut another large donut (2 pieces due to the dimensions of the foam) and stuffed it into the cover, creating an “all-foam” filter option that can easily be cleaned or replaced. 

As the foam I have is of unknown origin, and I haven’t tested this on a running engine yet (only a vacuum), I would be cautious in choosing this option. However it may actually be the simpler way to go.

Good luck with your project!

Marc Gagnon



I used to have a handle on life, but it broke.

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