The International Cessna^® 170 Association

The rings go inside the shroud, between the shroud and the muffler itself. They are on the engine installation page of the 170B parts catalog (IPC).

Miles, those aluminum rings your are discussing, are they the rings that appear to be made of lead or some other malleable material that goes around the short exhaust pipe between the cylinder and the muffler shroud (inside the shroud)? I notice on mine that those are missing and the shroud is somewhat loose at the back of the shroud. I am wondering if those not being there could be affecting the amount of heat I am getting in the cabin. My heater does a pretty good job at 40+ degrees, but when the outside air temp is below 40 it struggles to provide sufficient heat in the cabin.

Frank

The rings on the muffler shrouds help keep the air in the heat muff and ultimately in the cabin.
Any leaks there will reduce cabin heat but wont risk any CO poisoning.
If your's is a '52 or prior, they weren't really know for their ability to keep the cabin comfortable much below 40 anyway.

Are those muffler shroud rings readily available? Mine is a '56 172 (identical set up as a later model 170).

I have seen those rings in a catalog, but I can't seem to remember which one. If you can get part #s from the 170B IPC, you might try iwantcessnaparts.com. I don't remember them being ridiculously expensive.

They do have the look of lead, but I think that's just a result of the heat; they feel way too light to be lead.

There are 3 different part numbers. 0550157-29 is for the upper inlet pipes. 0550157-30 and -31 are the left and right lower seals. I don't know if it is depth, diameter or both that makes the lower different from the upper and I can not see why the left and right lower would be different. None of them are found when searching at IWANTCESSNAPARTS.COM.

They are listed in AWI's catalog as being available in overhauled condition. I remember them not being available as AWI developed their line of exhaust components but seem to remember they figured out how to reproduce them, at least in "overhauled" condition.

I don't think they truly seal as their name implies but rather take up considerable space at the edges of the heat baffle around the pipes. Many systems don't have them installed at all today probably because they are not readily available and most of us can't figure out exactly how to make them. Heck we can't even decide what they are made of.

Addendum: The 172 part numbers are the same for serial 28000 thru 47746. After that the system which I believe have a slightly bigger muffler but otherwise very similar, only use a two piece seal on the two top pipes. Nothing on the bottom. The parts for the newer 172 system are 0550176-22 and 0550176-45. These parts are available and might fit just as well but i doubt anyone will be buying them at the price of $578.20 and $33.44 each. Interest though that the notes on these parts list the metal ring as being aluminum and the packing that goes on top as a composite rope.

http://onlinecatalog.wagaero.com/app.php?RelId=6.4.6.4 pages 58 thru 60

I thought that Wag Aero had them but I don't see them in their catalog. It would be worth a call. They appear to be a lead based material as they are soft.

I also noticed Wag Aero will repair the Pancake Mufflers @ $399 each.

Dan,

Though a little off subject, Wag stopped repairing pancake mufflers years ago. Then recently they started advertising they will repair them. But recently a local owner sent his pancake to them for repair and they said they wouldn't/don't do them. He eventually had it repaired by a local welder.

So who knows if one would be able to get Wag to repair a pancake but I don't hold much hope should the time come to repair mine.

Bruce
Thanks, I would like to use Pancakes on my project someday so I might pursue that to see if they will. I was also very surprised to see Pancakes on their list.
Thx,
Dan

I just talked to Charlie Feld at Aerospace Welding in MN (George, he said tell you hello) regarding these elusive muffler/heater shroud seals. Charlie advises that on the Hanlon Wilson mufflers there should be three (3) of them. Two on top and one on the bottom and the bottom one is a different size than the top ones. He, like most folks, isn't sure what the chemistry is on the seals, but says he does have some serviceable ones in stock at $65 each Supposedly having those seals in place will help the cabin heating, but the most important thing they do is to act as a stand off to prevent the muffler shroud from riding on the heat studs on the muffler. Not having the "seals" could result in the heat studs wearing holes in the shroud. Charlie does not know of any company currently manufacturing these seals. He did say that at one time Acorn Welding, in Canada, had given thought to tooling up to produce these seals, but doesn't know if that ever happened. Sounds like a big price for such a small, rather simple item---guess that is one of the fun aspects of aircraft ownership

I'd consider doing something up as an owner made part.
There is a lot of high temperature materials out there that these can be made out of.

Frank and David, I took my mufflers to a local machine shop that did work for the RV guys. He looked the damaged seals over, took some measurements, and said no problem to make the parts to "my specifications" . This was more than 10 years ago and they are still working great. If I recall correctly, he used heavy wall pipe with an inside diameter that matched the damaged seal parts radius. Then he cut the pipe to the match the shape and thickness to match the difference between muffler and shroud diameter. It was quick and simple with his equipment and he charged me $175.

Bruce Fenstermacher wrote:There are 3 different part numbers. 0550157-29 is for the upper inlet pipes. 0550157-30 and -31 are the left and right lower seals. I don't know if it is depth, diameter or both that makes the lower different from the upper and I can not see why the left and right lower would be different. None of them are found when searching at IWANTCESSNAPARTS.COM.

Fellow 170 Guy's
0550157-29, 0550157-30, 0550157-31, Preferred Airparts show that they have a quantity of all three part numbers in stock, I have bought many parts from Preferred although their prices are on the high side compared to salvage prices they generally actually have in stock what they show listed at less than Cessna prices.
http://www.controller.com/list/PartsSea ... um=0550157
Preferred Airparts
Phone: (877)304-3592
Regards,
Jim

If I had a set of pancake mufflers, I'd be reluctant to spend a lot of money on welding. Due to the age of pancakes,they're bound to be seriously contaminated with exhaust products and welds are not likely to hold up very long. If the repairman can make and apply new material parts, that would, in my opinion, be the only way to go.

Here are a couple of pictures of NOS lower shroud seals. P/n 0550157-30 is around .75" tall -- it varies some in height as measured around the perimeter. P/n 0550157-31 is around .35" tall. The "fish mouth" shroud is a larger diameter than the left shroud,thus the taller shroud seal. They appear to be made out of 2 1/2" schedule 40 aluminum pipe (2.875" O.D. X .203" wall thickness). A quick look online found a foot of this pipe for under $25.