J, Ram K Air Cleaner Housings
Part Number
2406545 Versus 2120633

Are you curious?

In 1982, Dale Burkhardt made a summary table for Letter Car air cleaners and it says that the air cleaners
on the F, G, ram H, and J were the same (part number 2120633) and the ram K used 2406545.
I have always been curious about the difference between the two. On the same table Dale has a note:

Contrary to popular belief, most if not all of the 300K ram air cleaners were different from the more common '60 thru '63 variety. The difference was in a 1/2 inch change in the carburetor pilot which positioned the air cleaner relative to the air horn.

One day I went hunting for that 1/2 inch.
First thing I did was gather air cleaners and check if any had a part number stamped on them.
None did. Rats. That would have made things easy.

Then I set them side by side and looked for differences easy enough to see by eye. Nothing there.

So I got out a caliper and measured diameters, hole spacings, center to centers. Everything was the same.
I was stumped and put the project aside for a while. When I came back to it, I enlisted the advice of others.
It was Chris Pinder that shed light on the subject; the difference is not on the top side.

Turn the air filters over and look at the bottom side of the base, you will see these indexing plates.

If you compare the index tab on the top picture to the one on the bottom picture you will see the middle piece is different.
The difference is 1/2". Does 1/2" ring a bell?
And there is the answer;
It is the index tab on the base that tells if you have a 2406545 or a 2120633.

Here are the same pieces from a reverse angle:

These indexing plates fit over bosses on the carburetor tops and orient the air filter.
If you were to set two carbs side by side and set the air filters on top, you would see

and if there is a difference it is hard to tell.
Try a straight edge and then you can see how the air cleaner shifts on the carb.

So what does this mean to the car?
I went to the ram K with a 2120633 air cleaner (which happens to have a gold top cover) and a 2406545 (the chrome top cover).
This car has AC so if there is an issue with air cleaner clearance, this car would have it.
On the driver side, there was no interference but on the passenger side,

you can see the 2120633 is pretty tight to the AC actuator.

With the 2406545 filter, there is plenty of clearance.
And that may be why Chrysler engineering made the change.

but I am still curious........