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Permalink Reply by John Austin on August 25, 2020 at 8:25am

I initially tried high temp silicone caulk, but it would eventually burn up and then become brittle.  What worked best for me was to use some woven fiberglass caulking rope like that used to stuff in cracks around fireplaces, etc.  As I recall, I adhered the rope to the heater-side of gaps with high temp silicone caulk and then clamped the heater plenum against the muffler with the provided clamps.

However, I never really liked that system where an external plenum is clamped against the side of the muffler and you have all those potential gaps to seal.  I later deleted the Bing carb on Jab 3300 and also deleted the airbox, carb heat, and cabin heat systems and installed a Sonex/AeroConversions' "AeroInjector" TBI carb (which needs no airbox or carb heat) and installed a Robbins Wings cabin heat muff on the exhaust pipe. It has metal-to-metal end plates that tightly clamp the exhaust pipe and need no sealant.  I also wrapped it with exhaust wrap to improve efficiency.  Even though it is downstream of the muffler, clamped on the exhaust pipe, it works better than the original Jabiru FWF design!

John

N750A

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Permalink Reply by Carlos Sa on August 25, 2020 at 10:56am

Hello, John

Thanks for the comments, much appreciated.

I'll keep this in the back pocket, as the project is now on a strict "no-changes-diet" so I can finish it soon ("soon' being a very subjective term).

It's been way too many years, and "someone" wants the garage back...

Cheers

Carlos

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Permalink Reply by Brad Marcum on January 22, 2023 at 8:36pm

John, where did you source the heat muff?

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Permalink Reply by John Austin on January 22, 2023 at 8:50pm

I got it from a vendor called "Robbinswings.com" but I "think" they're no longer in business. Spruce sells something similar called a "Turbo" that looks to be an improved design.

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Permalink Reply by Roy Eichendorf 2 hours ago

Hi John,

Now that you've had your exhaust pipe muff for a few years, are you still happy with it?

All the reviews of the Turbo Heat muff on Aircraft Spruce are 5 stars. But I'm just wondering whether the extra weight might eventually crack the weld joint of the exhaust pipe to the muffler. Have you or anyone else experienced that?

I just received my Gen 4 3300 last week, for my 601HD project. Living & flying in western Canada, I wasn't confident that the Jabiru heat muff would provide sufficient cabin heat for my needs. So either I fabricate my own enclosure muff for the muffler, or else I buy the Turbo Heat. If you had this choice, which would you choose?

Thanks!

Roy Eichendorf

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Permalink Reply by John Austin 2 hours ago

All the reviews of the Turbo Heat muff on Aircraft Spruce are 5 stars. But I'm just wondering whether the extra weight might eventually crack the weld joint of the exhaust pipe to the muffler. Have you or anyone else experienced that?

Funny you should mention that!  I eventually DID develop a crack in the weld between the exhaust pipe and muffler - I believe the additional weight probably enhanced any vibrations?  I installed a new muffler/exhaust pipe and reinstalled the same heat muff, but this time I suspended the exhaust pipe just beyond the muff with an automotive exhaust hangar - one of those thick, rubbery straps - and secured it to the exhaust pipe with a stainless hose clamp and secured the other end an engine mount tube with an adel clamp.  This has worked great for hundreds of hours with no problems.  Also, rather than wrap the muff with the fiberglass  exhaust wrap, I got a single sheet of aluminized muffler insulation and fitted it to the muff.  It is secured on both ends by the muff hose clamps and I put a few safety wire loops every few inches between the clamps.  I like the idea of the smooth, aluminized surface as it is non-absorptive should either oil or fuel leak onto it.

One additional cabin heat mod I did was to install a 12vdc computer server suction fan  at the heat outlet in the cabin to boost the flow in extremely cold weather.  This works great but of course I think any muff on an exhaust component and/or suction fan on such a system makes a good CO detector mandatory!  I also have a few inches of exhaust pipe extension on my system and have never had a single whiff of CO!

So, yes, I'd go again with the "Turbo" heat muff - as long as the exhaust pipe is suspended.  Who knows, it might be more efficient so that the booster fan might not be necessary.

John

N750A

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Permalink Reply by Carlos Sa on August 25, 2020 at 10:59am

In case someone has the same question, I contacted Permatex.

They recommend this:

Permatex Ultra Copper Maximum Temperature gasket maker, product 81878 (US).

Looks like the product number in Canada is 59703, as a search for 59703 on their site produces 81878.

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Permalink Reply by John Austin on August 25, 2020 at 11:32am

Let us know how the copper works out.  If it still burns out, try adhering the heat muff to the fiberglass rope caulk.  Even the fiberglass caulk will eventually burn out or at least become brittle, but it lasts much longer than anything else I tried.

John

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Permalink Reply by Carlos Sa on August 26, 2020 at 8:57am

Correction: Permatex Ultra Copper Maximum Temperature gasket maker max temperature is only 700 F.

Permatex 80335 Muffler and Tailpipe Sealer will withstand up to 2000 F.

Sold in Canada as Permatex® Spider Patch™ Exhaust Joint & Crack Sealer 90335, but the packaging says "VersaChem":

https://www.canadiantire.ca/en/pdp/permatex-spider-patch-exhaust-jo...

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