Exhaust port corrosion

How to keep the Cessna 170 flying and airworthy.

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BernieS
Posts: 1
Joined: Thu Sep 15, 2022 11:59 pm

Exhaust port corrosion

Post by BernieS »

I was doing some exhaust work on my C-145 and discovered some mild corrosion around a few exhaust ports where exhaust gases had been leaking past the gasket at the port. Does anyone recommend any type of sealer to add when I install the new gaskets? Also, what brand of gasket do you all prefer?
Many thanks,
Bernie
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Bruce Fenstermacher
Posts: 10320
Joined: Tue Apr 23, 2002 11:24 am

Re: Exhaust port corrosion

Post by Bruce Fenstermacher »

By port I assume you meant at the cylinder head. I would only use "No Blow" style TCM PN 627429 or equivalent after market makes no difference, buy the least expensive.
627429.png
627429.png (73.38 KiB) Viewed 2013 times
https://www.aircraftspruce.com/catalog/ ... -11230.php

Note: You will have to custom fit each to it's cylinder by grinding some metal away for clearance to the next head or intake. Some need it others won't. These are reusable and last a long time.

You don't use any sealer of any sort. Slip joints get anti-seize compound.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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cessnut
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Joined: Thu Apr 08, 2021 12:36 am

Re: Exhaust port corrosion

Post by cessnut »

A fairly common misconception is that installing a spiral wound gasket will magically solve exhaust leaks. If the exhaust port or the riser flange are not perfectly clean and level, a no blo gasket will not seal. It is also a good idea to evaluate the health of the studs while the exhaust is removed. Do not use sealant. Obtain a copy of M-0 and follow it.
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GAHorn
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Joined: Fri Apr 12, 2002 8:45 pm

Re: Exhaust port corrosion

Post by GAHorn »

Bernie, Welcome to the 170 Assc’n Forums.
The good news is you’ve found the source/reason for the exhaust leak.
The bad news is…. if the cylinder exhaust flange is eroded…. it must be re-surfaced before the leak can be stopped. Gaskets and sealants will not stop a leak caused by eroded cylinder exhaust surfaces.

There is a history to the methods used to resurface that area on a cylinder…. Back when cylinder rebuilding was a profitable business.. cylinders were often removed and the area built-up by welding, then machined flat again. This was usually done in conjunction with grinding cyls oversize or channel-chrome/plating to renew the I.D. back to standard. These processes are not often performed since new cylinders became popularly supplied by aftermarket companies like Superior, E.C.I., and others. By the time those processes are completed the difference in price from new cylinders made complete replacement more popular. Here’s an Aviation Consumer article on the subject:

https://www.aviationconsumer.com/aircra ... -worth-it/

There aren’t many folks who will do cylinder overhauls, but if you wish to pursue it you might contact Gibson or Corona:

https://gibsonaviationok.com/cylinder-overhaul

or

https://www.coronaengines.com/Cylinder-Overhaul

Hope this helps.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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n2582d
Posts: 2827
Joined: Mon Apr 29, 2002 4:58 am

Re: Exhaust port corrosion

Post by n2582d »

Has anyone used the exhaust port resurfacing tool that Aircraft Spruce markets here? Although Spruce says it's available, the adapter plate for the Continental doesn't show up on their website. The tool is made by Sydow Tool Engineering Corp. The adapter is available on their website for $200.
Exhaust Port Surfacer.png
Exhaust Port Surfacer.png (82.3 KiB) Viewed 1850 times
Gary
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