The International Cessna^® 170 Association

I am in my 1st annual after owning N7A and my A&P IA pointed this out to me. I think it looks like corrosion to my novice eyes. Has anyone seen this before? Is the best bet to replace the entire carburetor?

Looks like this is the current model I would need to replace it. 10-4895-1

Quality Overhauled MA-3SPA Carburetor, Continental 633029, $959 + $600 Core
Overhauled Marvel Schebler / Volare(Facet) / Precision Airmotive aircraft carburetors.
For Use On: Continental O-300-A, O300-C, O-300-D, C-145
Supersedes: 10-3237, 10-4439, 10-4439, 10-4895
Factory Overhauled

Aaron, if you looked at the carb you would notice there was (or should) be a steal brace that supports the mufflers and bolts to the carb mounting. I think that is the (black) steal bar in your picture. Years and years ago, well before I was involved with 7A, that brace broke, hung down and wore that hole in the carb base. It is not corrosion.The bracket was removed and 7A flew for 20 years without the bracket until I replace it. I'd bet that carb has operated flawlessly with that wear for more than 40 years. It has no effect on the operation.

It has not ever been been a concern of any mechanic inspecting 7A. I'd forgotten all about it in fact until I saw your picture. Perhaps once your mechanic understands how it got there, he won't be concerned either.

BTW, should you decide to replace it, and they won't except that one for a core, we may have another "core" you could have. I'd have to look and see what is in the stock pile of aircraft parts we have.

I have to admit I was totally confused by the picture. Local corrosion? Bruce’s explanation is understandable.

If you want a steel exhaust brace I have one that you can have for postage from Canada.

Charlie, he should have a steel bracket. At least there was one on it when it left my possession. The bracket that caused the wear broke and did its deed at least 40 years ago and was removed till I replaced it.

Also I didn't realize at first, the larger wear at the bottom of the photo, is a blown up inset of the area above it.

Fill that hole with JB Weld (after cleaning it with aerosol electronics cleaner.)

So it broke off then the end lodged against the carb base and as the muffler exhaust tubes moved in flight it bored a hole or at least tried to make a hole. Nice . Definitely had me stumped.
George JB weld to make it look perdy ? Kind of like that.

Jim, you got the picture.

Looking at Aarons picture, it looks worse than in real life. At least that is how I recall it in real life.

Thanks Bruce, that really helps. It doesn't look great but it also doesn't look like it is about to crumble or fall off. I'll pass the info along to my mechanic and hopefully he'll be satisfied with cleaning it up really well and filling the hole. If not I may need to take you up on the core.

Do you recall when the Carb was overhauled last? Since the mechanic has the logs I can't look it up at the moment. Is it something that is done "as needed" or is an overhaul after a certain number of hours best practice? I'm still new at this and trying to find the reasonable balance of preventative maintenance and "not fixing things that ain't broke".

Not answering for Bruce… but generally Part 91 carbs are done “on condition”. But a full “overhaul” of a powerplant would imply overhaul of all accessories. (a reason most so-called “overhauls” in general aviation are actually “major repairs” only.)