Can / should / how to clean air filter

[stuartrubin]

TLDR: Can I or should I clean my engine air filter?

Long version: I re-jetted my 34ADF carb and while I was at it, I replaced the engine air filter which was old, cracked, and dirty (at least i think it was dirty). The air filter is a rectangular "lunch box" style. The new one was a not quite a perfect fit, but in my opinion at the time, good enough. After rejetting, I did a very cursory re-setup (I mean I barely turned the mix, idle speed etc.) and things seemed to be running fine, except that my idle speed was high. (I chalked this up to lack of adjustment). Also, it would take a few cranks to get started. But the real problem was a very rare engine stall. For no apparent while running it would stall and take a few cranks to get going again.

Today I finally got a few minutes to play with the carb adjustments. On a whim, I put the old air filter back on and it seemed to run a lot better!

So, here is my theory: the new, misfit filter was restricting air flow. This worked OK while the car was warming up, effectively acting as a choke. Once I got going, I was staring for air, which caused an occasional stall. Does that make sense?

Assuming that the new filter is actually problematic, can I clean the old one? It seems "grimy" but does not have visible debris or anything, just old. Should it be degreased? Or maybe it needs the oil film on the filter?

Thanks!

Stuart

[18Fiatsandcounting]

You mentioned that the air filter is the rectangular lunch box style, but what is it made of? Paper, or some kind of plastic foam? If it's paper, I'd just replace it although sometimes I have been able to somewhat improve a dirty filter by shooting compressed air through the filter element from the inside outwards (opposite the normal air flow).

If it is a spongy foam type of filter, you can sometimes soak these in soapy water and wash out the oil and greasy stuff. Eventually they just all apart, though.

You mentioned a high idle speed. That can sometimes be an air leak into the intake manifold, so maybe a hose or something got knocked loose when you changed the filter and did the adjustments?

-Bryan

[stuartrubin]

Bryan, thanks for the reply. Sorry it took so long, but here is some more info.

As for the high idle, and general crappiness of the ride, it turns out that last time I was messing with carburetor, I did not properly re-install the choke assembly. I have an "automatic" choke which is controlled by the engine coolant temp. The spiral spring was not engaged with the choke lever, so the choke was never engaged. No biggie...

And my idle speed it fine now. For fun, I sprayed some carb cleaner around to see if I could detect a leak, and there does not seem to be one.

But, I still would like to clean the filter. It looks and feels like "felt". Maybe more like paper than foam. I don't mind replacing it, but I just can't find the exact fit. Here are photos. Maybe you can suggest which cleaning method to use, or where to get the right replacement. (Like I said previously, the one I bought was close, but really not a great fit.)

Thanks again!
-Stuart

[18Fiatsandcounting]

Stuart, are you sure that's an air filter and not an oil filter?

All kidding aside, this filter is pretty grungy and I would not try to clean it. It looks like it has some lettering or numbers on the rubber seal, so have you tried Googling those to see what you come up with? Or does it just say "Hecho en Mexico" or the like?

Any chance this fits? https://autoricambi.us/air-cleaner-repl ... ment-1-75/

You could also take it to a good auto parts store and see if you can find a match. Rectangular filters are fairly common, so there may be something for another car that would be close enough. As long as it seals OK, you're probably good. If you are really creative, you could find a larger filter (with the correct height) and then cut pieces from the sides to get to the right size for you, and glue the cut sections back together. This is an extreme solution, so I would only do this if there are no other options.

-Bryan

[Integrale]

If you've got hood space this K&N may also fit: https://www.amazon.com/3952-High-Perfor ... 228&sr=8-2

This one is probably the stock size: https://www.knfilters.com/e-3951-rectangular-air-filter