Air Filter?

[jeepguy1948]

I tried running an air filter with my stock Zenith carb however the engine ends up running rich. Has anybody ever experimented with a smaller jet to correct that? I don't need to hear from people who want to tell me that "if Henry didn't put one on it doesn't need one dangit!". This is simply exploring what could be.

[jeepguy1948]

It rather surprises me that vendors are actually selling the air filters since they won't work.

[Bob C]

You need to air balance the carburetor to run an air cleaner.
Scroll down the link for info on air cleaner.
http://www.rennerscorner.com/carbure...formation.html

[nkaminar]

Bob C has the right answer. To make this easy to understand, the Model A carburetor has the fuel float chamber connected to the outside air. When you install an air filter it acts like a choke to make the fuel/air mixture richer. To avoid this you have to connect the float chamber to the inlet side of the carburetor so that it sees the pressure reduced by the air filter. You can do this by running a line from the air bleed at the top of the float chamber to a point just before the choke plate. You have to do some drilling and tapping and run a rubber or metal tube. It is a good project for a detail oriented engineer type person.

You can try running a smaller jet but as the filter becomes dirty it will change the fuel/air ratio. The fuel/air ratio will also change as more or less air is sucked into the carburetor at different speeds. The fix is to run an air balance tube.

[Mulletwagon]

I run a high boy with a K&N filter on an unmodified carb and it works fine. Our rides are really too valuable and cherished to run without a filter - IMHO.

[old ugly]

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there is an option of running an oiled screen type filter instead of paper.
it is not as restrictive but will not filter everything. it will keep larger stuff out of there ( rocks, insects, mice, birds).
i have used them without doing any modifications.
if you are driving pavement none dusty roads it may work for you

[BillCNC]

This is what is done to air balance a carb.

Original bowl air vent is plugged with a set screw.
Venturi has a channel machined into it for passing air from air horn to bowl.
Slot machined over the secondary well for air passage.
Hole drilled into air horn for air to travel to bowl.

Carburetor has stock appearance.

Regards
Bill

[Synchro909]

All 4 of my cars sport an air cleaner. I have tried to pressure balance an original carburettor just as BillCNC shows but it was a fizzer. I blocked it all off and it now runs well with air cleaner fitted. That said, I haven't given up on balancing a carby but not now. I can't see the point of fiddling with what is working.
BTW, with my cars, being RHD, I cannot use the air cleaners you guys do so I make up a "manifold" to carry air from a large paper element unit mounted on the radiator stays to carry the air to the carby's intake. That is not easy because the steering column and choke rod are in the way. I think the large size of the air cleaner helps.

[nkaminar]

Bill, that is pretty clever. I like it.

[dennis lumbert]

I use a highboy with K&n filter on stock Zenith or Tillotson with no issues.

[Sunny the Model A]

I purchased a high-volume filter from Smith and Jones, same one as Snyders, since it has such a large filter, and does not appear to be a restriction compared to the smaller filters. Is it really necessary to try to balance the carburetor? Wouldn't tuning the enrichment screw on the carb be sufficient?