I don't think you need an air filter, even on gravel roads, as I hope you have a stove around the exhaust pipe, connected to the carburetor end with a flexi hose (55 cm). Then you don't need any filter. If missing, you should install that(original) system and you don't need to worry about dust, etc. even driving on gravel and sand.

The heated intake air will also help to get a correct temperated mixture of gas and air, which gives a good combustion.

Quite a few of the 4-cyl. oldies miss the pre-heating system, and due to that, get into trouble when driving. I bought some NORS stoves from Gary Wallace to help out here in Norway.

CORetiree,

I think you could probably change the heat stove on the exhaust
manifold side. It has one hole for the tube out to the carburetor, why not have one tube in at the top connected to an air cleaner?

Maybe heat rising from the heat stove might cause heat at the aircleaner, so a tube would be needed to keep the aircleaner far enough away.
The other problem may be the extra restriction caused by the aircleaner , so it would need to be a low restriction type.

I see your point when you already have the stove connected to the carb by a flexi hose, and still want an air filter. By the original system the main part of the air stream is "protected" against the dust. But (as to my memory) the opening on the choke part of the carburetor could make it possible for dust/dirt to creep into the carb and make trouble.

I don't have any tecnical solution to avoid that, but may be a part of a pair of nylon stockings could be of help. In 1963 we used such stockings in front of the intake to my 29 A-F**D. Went very well, but I cannot longer remember if we rolled it to a ball or made a screen of some kind. You better try and let's hear the result.

So far I have not experienced trouble when driving on old gravel roads, wet or dry.

I bet you could use some filter medium out of a fiberglass furnace filter and stuff it in the hot air tube. I would oil the filter and use a piece of wire to pull it out and check it once in a while. Wouldn't be visable and would be better than nothing. Plus the heat stove could still be used. Just a thought.

I would think the heat would melt the fiberglass and oil would give off fumes

I would use the 600wt oil since it tends to stay put and if the fiberglass is stuffed down inside the tube so it won't touch the exhaust pipe inside the stove, it shouldn't get that hot or even use a course steel or bronze wool and cover the carb side of the ball with cheesecloth to keep metal particals from going to the carb. I have also thought if the hot air tube by itself was oiled with 600wt on the inside it would trap a bunch of dirt. That 600wt is pretty sticky stuff.

If you should add anything to the air system, you must add it near to the carburettor itself, to lower the impact of the heat. Oil near or inside the stove will certainly make your driving not very nice until the oil has dried out.

Some times the original solution is the better one, I think.

I have the same concern about no air filter on the intake. I stuffed an oil laden ChoreGirl (pot scrubber) in the tube just in front of the Carb. It does catch some dirt and I clean it often.

Just as a side note to those that are interested, as of October 1, 2010, Cars & Parts Magazine no longer exists.