Van's Heat Muff Problem

[Rick6a]

I would encourage anyone using Van's stock "heat muff" to periodically examine the exhaust pipe it is attached to. When I removed the muff because it would not generate any observable RPM drop when carb heat was applied, I was dismayed at the deepish gouges worn into the crossover pipe it was attached to. TT 220 hours.

I replaced it with the more efficient Wicks muff. Obscured from view in this photo, it is attached to the crossover pipe directly behind the damaged pipe. I now observe at least a 30 RPM drop when carb heat is applied.

 

[Geico266]

Good catch Rick. I'll be checking mine next oil change.

 

[gasman]

Upgraded mine for that same reason............

 

[wilddog]

What is the purpose of the air gap on the bracket the SCAT hose attaches to and the top of the FAB?

 

[L.Adamson]

What is the purpose of the air gap on the bracket the SCAT hose attaches to and the top of the FAB?

To allow some additional warm air from the cowl area. The scat tube diameter doesn't have enough area. This is the result of an icing incident.

L.Adamson --- RV6A

 

[RV7AV8R]

Rick6A, I am doing may annual and saw your picture so I checked my stcok Vans heat muff on my rv7 O 360. After 300 hrs there was not even enough wear on the exhaust pipe to feel with my fingers. Visually I could see where it rubbed on the pipe but no wear. I had it on pretty tight maybe that is the trick to avoid wear.

 

[DanBaier]

Van's Heat Muff

Had the Van's heat muff - when I saw this thread, had about 48 hours on the airplane. Pulled the muff, and initially it looked very much like the photo in the opening message. On closer exam, the scratches were slight and polished out on a scotchbrite wheel. Larry Vetterman told me that in light of that, he doubts that there was any damage.

This was a fortunate catch - I don't think it would have been long before serious repair would have been required. I went with the Wicks heat muff and I feel a lot better about that design - although I have to say I haven't seen much indication of carb heat with either system.

Larry had told me that one fix would be to return the pipe and let him cut off the offending part and weld in a replacement. Larry's guidance was that anything on the pipe must be on tight and I got the idea that he's seen this problem before.

Dan