Exhaust Shroud Seals - Who has them in Stock?

[sea1dww]

Hello All

I was adding a new egt/cht instrument and asked my mechanic to inspect the mufflers while he had the cowling off, as the exhaust sound was getting a little louder.

He reported back to me that the right muffler had a hole in it the size of a tennis ball! I wonder how I survived these x/c's I've been doing lately. CO poisoning would seem the probable outcome as that muffler feeds my cabin heat! I'm really concerned about this as my stickon CO detector did not indicate an issue. As I am not fond of marginal parts that might kill me, I decided to change both mufflers at the same time.

The problem I've found is in finding the Shroud Seals. I need 4 seals for the risers on the top and two different seals for the left and right outlets on the bottom.

If anyone has these seals or knows where I can find them, I would appreciate the help.

Dave
'54 B
N1946C
s/n 26091

[Jr.CubBuilder]

I've had the same problem, and I haven't found a source, so please post something if you find a better solution.

At some point earlier in its life someone sliced some thin sections off the end of some kind of pipe, then squished, bent, and hammered them around something of the same approximate diameter as the exhaust can. Since I couldn't find anything better I put them back in under the heat shroud. The space between the shroud and the muffler can is under positive pressure while the plane is moving so in theory at least this pressure out to be pushing air out around the various leaks. This seems to work, but I'm not completely satisfied with it. I've thought about sealing up the top two with exhaust grade RTV or something similiar, but it's a time consuming task, I don't have a hanger, and I haven't gotten around to it. I'm guessing that they origionally had some nice asbestos gaskets that sealed up nice and tight when they got squished under the shroud.

[Bruce Fenstermacher]

No Jr those thin sliced pieces of soft lead like pipe bent around something ARE the seals.

At the convention I saw the new ones AWI is making to sell with their muffler assemblies and that is when it hit me.

They are just thin sliced pieces of soft (like lead or soft aluminum) pipe bent around something.

BTW I'm not sure AWI is satisfied with the product (seals) they had sent because there was a note with them questioning if we felt that what they had provided was a suitable seal. I got the impression that the jury was still out as to whether they were going to sell them (seals) or continue to look for something else.

If you call them MAKE DARN SURE you mention you heard about their products from the convention and you really appreciate their VERY generous donation of a complete (and I mean every thing) exhaust system and heat muffs for a 170.

[sea1dww]

I spoke with AWI today. They had the mufflers, but no seals. They did give me a very generous discount on the mufflers and shipped them out the door today. They seem to be good people and know the association and Mr. Horn well.

[GAHorn]

The seals are made of soft aluminum tubing....NOT lead or asbestos. Charlie Field at AWI was looking into making them. I'll follow up with him on it, but it's really not difficult to make them. Cut them out of thick-wall alum tubing, and press them in a hydraulic shop press.

[MoonlightVFR]

Exhaust Shroud Seals?

I think I am about to learn something NEW.

In 1973 I was informed that these were a HEAT SiNK to prevent cracking of the muffler at inlet juncture. In fact they are not installed between the muffler and Shroud on my 170B w Hanlon Wilson system they are simply on top of the Shroud.

I am rather concerned now when CO is involved in the thread.

Are there any 170 owners flying without these parts installed?

This has always been a part that I viewed w a little mystery.

I now am thinking SPACER but reading SEAL in this thread.


The Shroud of Hanlon.


regards

[Bruce Fenstermacher]

I'd use the term seal rather loosely here. They don't really seal but take up some of the room around the exhaust header and the heater baffle which surrounds the muffler.

I suppose if they where brand new, never been dropped on the floor and you custom fit them to your muffler and heat baffle maybe they would seal.

I'd doubt if not having them would lead to more CO from a muffler leak. In fact since it should be somewhat more difficult for any CO to escape out of the heater system with them installed as they should be. So your more likely IMHO to have a CO problem with them than without them.

[cessna170bdriver]

The 170B IPC does call them "seals", but I agree that "spacers" is a more apt term.

Miles

[GAHorn]

They do not prevent CO from entering the cabin heat system. They assist is "sealing" the muffler shrouds against leaks...but not like you guys are thinking... The purpose is to prevent execessive heat loss of cabin and carb heat from the higher-pressure area inside the shrouds ... out to the lower-pressure area outside the shroud...hence their nomenclature: "seals". (They reduce the loss of heat to atmosphere. They are not a safety item and many systems operate just fine without them.)

[sea1dww]

Yesterday I received 5 of the six seals I ordered. They couldn't come up with the lower left seal, so I hope I won't need it when we install the new mufflers that arrived yesterday as well.

The seals looked awful. They were obviously freshly made, but they looked like Bobby Joe was messing around in the barn with a hacksaw and a hammer. I'll have to get out my dremmel tool and knock off all the burrs and sharp edges. I haven't checked them for fit yet and I'm a little concerned by just eye balling them. The exhaust tubes are round and these seals are oval. hmmmmmmm?

I'm looking forward to the security in knowing I have a completely new stainless steel exhaust system though. I think I'll have a sense or feeling of safety from CO. (Yet not so safe as to not keep my CO sensors fresh) I'm also looking forward to a much quieter engine noise.

I've only been grounded for 10 days and I'm already going through flying withdrawal. I'm taking Monday off work and I will deliver the parts to my mechanic and wait patiently for the test run. After which, I'm off to the San Juans for lunch.

Dave
N1946C

[GAHorn]

Yesterday I received 5 of the six seals I ordered. They couldn't come up with the lower left seal, so I hope I won't need it when we install the new mufflers that arrived yesterday as well.

The seals looked awful. They were obviously freshly made, but they looked like Bobby Joe was messing around in the barn with a hacksaw and a hammer. I'll have to get out my dremmel tool and knock off all the burrs and sharp edges. I haven't checked them for fit yet and I'm a little concerned by just eye balling them. The exhaust tubes are round and these seals are oval. hmmmmmmm?

I'm looking forward to the security in knowing I have a completely new stainless steel exhaust system though. I think I'll have a sense or feeling of safety from CO. (Yet not so safe as to not keep my CO sensors fresh) I'm also looking forward to a much quieter engine noise.

I've only been grounded for 10 days and I'm already going through flying withdrawal. I'm taking Monday off work and I will deliver the parts to my mechanic and wait patiently for the test run. After which, I'm off to the San Juans for lunch.

Dave
N1946C

The NOS seals I've seen looked exactly as you just described the ones you have... very rough around the edges and not quite circular. Since they're soft aluminum, I doubt that's an issue. They'll smooth out with vibration shortly, I expect.

[sea1dww]

"Its hard to remember that your original intention was to drain the swamp, when you're up to your *** in aligators."

My original intention was to add an EGT/CHT/OAT gauge to replace my defective EGT. It is now installed with the OAT probe installed in the plug that filled the former Venturi inlet. I had to use a Spark plug gasket probe for the CHT as my relatively new Continental cylinders do not have CHT probe wells. The EGT probe is mounted 1-1/2" down the ehaust riser of the most rearward cylinder on the right hand side.

It sure feels good to know that new and accurate gauges are available for proper leaning and new exhaust hardware for proper exhaust scavenging and disposal.

These are just two more of the things that the prior owner failed to tell me about on his "Well Maintained" airplane. Once again, don't make the mistake I did. Verify everything before transferring money to a seller. I've spent nearly $5,000.00 fixing things that I was lied to about, and I still haven't gotten to the avionics.

Fortunately the airframe has potential, and eventually with some TLC and a bunch of money 46C will become a source of pride and a great representative classic airplane.

Dave
N1946C

[sea1dww]

I'm flying again, and what a difference the new mufflers make.

I have two of the new top seals left over as my others were servicable. If anyone needs them, send me a note and we'll work something out.

Dave
N1946C

[czollars]

Has anyone found a good source for these " seals" ? The part numbers 0550157-29 and 0550157-30 and -31. I'm sure this topic comes up from time to time. I'm overhauling my O300 and the left muffler is totally missing the seals. Does AWI now have a PMA on them? After reading the many posts, it appears they are not really a safety item.

I tried taking 3" OD (1/4" wall) aluminum tube stock and cutting a saddle shape in the end with a 4" diameter hole saw. That's the same diameter as the muffler. That didn't work too good. I'll try bending them next.


Thanks,
Chris

[Bruce Fenstermacher]

Chris if I was to try to manufacture them I'd slice the appropriate thickness of the end of a soft tube of the correct diameter and then bend it to the shape required to lay flat on the muffler.