Brian......In response to your question. It's my observation that they are being installed both ways with a tendency toward the auto type clamps. When you used to order a clamp from Univair they sent you the green-painted clamp I described. For some years they've been sending the auto clamp, I believe.
Considerable thermal stress is set up on the joints at the "muffler" and at the cylinders as they heat up. My Alon, which used stainless stacks, had a tendency to crack where the two stacks on a side joined. Something has to give. I'd guess that those who are not having any problems have enough give in the system. If you look at the cowl hole on some coupes you can see fretting where the tailpipe rubbed. Also the long regular steel stacks probably have some give, too. When I used auto clamps I couldn't get them tight enough to keep the pipe centered. I also did the final tightening with the engine "half" hot after a flight. Good Luck! Two final observations. I was told by an IA friend that any welding on an A/C exhaust system was a "337" repair. I've never tried to verify that. The other, Uncle Fred wasn't stupid when he designed the Coupe with the noisy exhaust pipe out the "passenger side", was he? Cliff.... At 06:41 PM 5/13/99 -0700, you wrote: >Cliff, > > It seems I have a clamp which make the muffler tight to the stacks. > >How are others currently attaching it, today? > >I just installed the new ones that Univair sent me, I don't want them to >fail! > >Brian > >----- Original Message ----- >From: Cliff sinclair <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]> >Sent: Thursday, May 13, 1999 2:09 PM >Subject: [EMAIL PROTECTED] > > >> Brian...re your message on muffler experience. Don't know if you're >> using auto muffler clamps or not. If you are I offer these comments for >> what they are worth. They're based on past discussions with Uncle Fred >> and Leonard. >> >> If the muffler is bolted solidly on each end to the exhaust stacks with >> auto type clamps you have a rigid assembly. The (relatively) heavy muffler >> is suspended on two (long moment arm) exhaust stacks. This assembly is >> subjected to temperature change stresses and vibrations from a shaking >> and vibrating engine.It was originally intended to flex. My IA friend once >> told me that if I could be under the cowl and hear that engine I wouldn't >> fly behind it! The muffler also sets up vibrations from the exhaust gases >> pulsing through it. I found that these clamps grooved the muffler end >> pieces and made dissambly difficult. >> >> In earlier coupes the exhaust clamps were made of flat, thin steel maybe >> a half-inch wide. A peg about three-sixteenths in diameter and a quarter- >> inch in diameter was welded perpendicularly to the inside of the clamp. >> The muffler was installed and the exhaust stack was centered through the >> cowl opening. A hole the diameter of the peg was then drilled through >> the muffler flange and stack on each side. the clamps were then installed >> with the peg in the hole.There was no attempt to "cinch" the flange tight >> around the stack end. The shallow groove didn't let you. >> >> This worked fine until the peg wallowed out the hole, which it always did. >> Then a "positioner" was developed to cure that. It may have been used >> initially. This was a rubber/fabric piece about 3 to 4 inches long, 1 inch >> wide and about one-fourth inch thick with end caps of thin sheet steel >> riveted on. A large clamp was secured to one end that fit the muffler >exhaust >> pipe. A small clamp was fastened to the other end that fit the engine >mount. >> This device was then installed and positioned to center the pipe in the >hole. >> >> What about exhaust gas leaking past the muffler ends? Apparently this was >not >> a problem. The firewall must be sealed carefully anyway and the heater >inlet, >> which is not a perfect seal, is kept under positive pressure, relative to >cowl >> air, by the ram air from above the engine baffles. I always kept a carbon >> monoxide detector fastened to the panel anyway. Best Regards >>
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