National Aeronca Association Bulletin Board

My mechanic and I have decided that the Stromberg NAS-3A1 carb in my L-16A needs some major attention. I want to have it rebuilt and yellow tagged or to replace it with a direct bolt-on Marvel-Schebler. There apparently aren't many places that rebuild these old Strombergs and that have the equipment to fully bench test them. What I need is some guidance on identifying these repair stations and some recommendations for who does really good work at a reasonable price. I would also like some input and advice regarding replacing this carb with a Marvel-Schebler re: eligibility of a direct bolt on model for the C85-8F, the value of my Stromberg core in an exchange, and any other information/advice any of you can pass along. Any help would be greatly appreciated.

Try Bob Kachergius A&P / IA in Orland Park, IL
He will do the overhaul for $850. uni-tech@earthlink.net

His phone number is 708-267-7111
13221 Windward Trail

Personally, I would rebuild the Stromberg. Old time mechanics I have met prefer it...IF its in good shape. I am not a mechanic but I've listened a lot. I had one on my 85 and it worked fine. Best, JP

There is a good article in the recent issue of Aeronca Aviator (Vol. 18, No. 2, Oct. 2012)on the NA-S3 Stromberg Carburetors. Most of the discussion is focused on the mixture control and how it works.

I rebuilt my own. Haven't run it yet, but it's been full of fuel for a few weeks and hasn't leaked a drop. There is a considerable amount of info out there, and I have amassed enough to fill a loose leaf notebook. Spoke to one overhauler who wanted to do away with the mixture control. However, at 6,800 ft here, I didn't want to do that.

Took me several days to do everything, but I am comfortable with the results. It is a very simple carb and all the parts are readily available (I reccommend Fresno Air). I found a nice pic of a flow device here that I modeled mine after. You would need to build one of those and a fuel level gauge. Good luck, for $850, it might be worth a try.

Brian Walker
7 AC-DC

Article about Stromberg carbs a few months back saying that some were machined incorrectly so that float would not function correctly. AS I recall 6 were overhauled, 2 were found to be faulty and were corrected. This article was in the Aeronca newsletter. JP.

Most of these aircraft carbs are 'dirt simple' and I think the carburetor on my "H" Farmall is probably more complicated. I've overhauled everything from Carter four barrels to 'two story' Holley's in my younger days so it probably wouldn't be a problem to overhaul a Stromberg BUT I don't have the piece of paper that says I can legally do it so I send mine to Bolduc in the Twin Cities. They always seems to do a good job although a bit expensive.

Part of the problem with any updraft system is that any intake leak or fuel port restriction shows up as lean condition (cough, spit ) right away when trying to accelerate the engine, especially off idle and Strombergs without an accelerator pump are especially prone under cold conditions even when set up right. I've found that either leaving the primer out a bit or carb heat on until things warm up helps.

I have a Stromberg for sale right now on EBAY for anyone who might be interested.

Mikeb

Simple as they may be, if not machined correctly when originally manufactured, they do not function correctly according to the article. This flaw in manufacturing doesn't allow the float to work correctly although it does work. I would think Bill Pancake would know a lot about this also. JP

JC,
I think my point was working on these carburetors is not brain surgery. While I'm not disputing the point (because I don't know for sure) I find it hard to believe that something like this has been on the market for 60+ years and only now known to be 'defective'.
Mike

The article explained that YES! Your carb. WAS OLD but.... If the float was incorrect, although you flew it, it was n ever operating at peak efficiency or.....it was running too rich or too lean. The article went on to say that it often resulted in one Aeronca (for instance) out performing another in takeoff or climb when the two were identical. I'm sure the article is available and it seemed sensible. I hope you can find it and see what you think after reading it. JC

The toughest thing on these little carbs is setting the float levels. They are dirt simple but an improper float setting effects the operation over the complete range. If possible set-up the float using the aircraft it's installed on. I use an adjustable table next to the plane, just swing it over and work on it. After you get it to the correct level go get a couple cups of coffee. When you get back the level should have stayed EXACTLY where it was set. Once satisfied safety it up and go fly.
Fresno Air Parts can supply you with everything you need.
Paul