FYI,  UL mufflers (at least for the 350iS) now come from the factory with a reinforcing gusset to the exhaust pipe flange.  I repaired my original (which had cracked), but ordered a new one in the event of future cracking/needed replacement.  Likely was a identified issue...

Views: 1185

Reply to This

Replies to This Discussion

Thanks David. I did sand down the inner muffler side but still way off. I’ll try the old squeeze method with a 1-3/4” exhaust clamp. 


All good. Had to use a 1-5/8 clamp but just kept tightening, rotating and tightening again all around for the first 3” and it now slides in easily but snug. Now just have to get the spring loops welded on.

Looks like I have the newer muffler with the support bracket and through tube so hopefully can avoid the cracking issues.

John, consider cutting the length down a couple of inches after you fit up the cowl and see what you have for clearance from the underside of the bottom cowl.  You don't need much sticking out and it will reduce the force applied at the muffler flange by the tube.

How far outside the cowl is your pipe? I planned on about 5 inches raked towards the rear slightly but have seen many with a heck of a long run. 

I will measure and send a pic next time at hangar...

John, here are a couple pics.  Looks like about 6" extension from the cowl exit and approx 3" below the cowl at the end.  Next time I take the tube off I will likely take off another 1" of length.


I think there was a problem.

Mine cracked as well and had to be re-welded but  has since been fine.


Which style of muffler support brackets do you have?  The older ones that are shown in the Zentih UL-Power install guide show the brackets attaching to the motor mounts.

The brackets for my engine are much longer and attach to back of the engine case just below the upper motor mounts.

Tim, I had the older style which cracked after less than approx 50 hrs of engine time.  Ordered and installed the new version as you describe.  So far no issues and I thinnk there is much less bending stress on the bracket due to the increased length of the bracket and attach point on the engine.

The vibration from engine to muffler has to be different being attached to the engine verses the motor mount.   Hopefully ULPower did some statics/dynamics calculations to determine if this is better.

After having my cracked muffler welded 3 times in the course of 440 hours I ordered a new one from Wicks. Got it in about 10 days as they were out of stock. It is the new and hopefully improved version. We shall see!


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2022   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service