Muffler Shroud

[darhymes]

Installing new mufflers on my 170B SN 26754 and have run across some issues fitting the shroud to the muffler. The shroud pieces are Hanson Wilson (they look pretty original-rough, but serviceable) IPC Fig 51, items 45 and 47. The problem appears to be the flanges welded onto the upper exhaust tubes on the new muffler…they seem to “block” the upper part of the shroud and prevent it from seating properly around the muffler (the top of the shroud seats very firmly against the muffler while the lower portion is not seated against the muffler at all).

The previous muffler did not have these flanges but the IPC clearly shows them in place.

Just curious if anyone else has run across this issue or has any suggestions. To me, it looks like I could file away a small portion of the flanges to allow to shroud to fit better. I’m waiting for my IA to look at it but figured I may gain some insight beforehand.

[GAHorn]

Dustin,…the terminology you’re using …”flange”…. do you mean the “studs”….?? (which are intended to increase surface-area for better heat-transfer.)

You wrote that the previous muffler did not have them..?

It might be helpful to know that later 172 mufflers …which will fit onto the same engine…. did not have the studs. If your shroud was originally mated to a non-studded muffler…that may explain why it doesn’t fit well to a studded muffler.

[darhymes]

I got it figured out. Ended up tightening the screws along the top of the shroud, loosening them up and then working the shroud upwards while squeezing the top. By tightening the screws, the shroud was able to push against the flanges and slightly form (or deform-depends on your post of view) around them. The second time I tightened the screws, everything fell right into place.

I wish I had some better words to describe the “flange”. It is the horizontal ring that is welded onto each of the three vertical tubes that protrude from the muffler. If I could guess it’s purpose, it would be to keep the shroud from contacting the exhaust clamps (which sit directly atop the flanges). It was a new one on me since the previous muffler did not have this feature.

At any rate, problem solved. Thanks for the attempt to assist George.

[GAHorn]

Actually…I’d agree to the “flange” as descriptive of that “ring” on the riser. Thanks for clarifying for me. I believe the flanges are to help captivate the heated air and reduce leakage there. There originally was also an aluminum “seal”…. (Items 12, 13, 40, etc in the pic Fig 51 of the B-model IPC) ….a specially-shaped ring of aluminum ….intended to assist in keeping the warm air from leaking-out at those risers… but in many installations they are missing. I believe AWI makes them but they are not inexpensive, especially for “what they are”. The ‘53 and later B-model systems works “fine” without them.