The heat muff provided by Van’s has the inlet and the outlet on the same side of the heat muff. For my installation this would not work. I tried every conceivable location for the heat muff. Without building a new custom muff, the only location that would work was coming off the #1 exhaust. This was fortunate for the air inlet, but not great for the outlet back to the firewall.

I cut the muff in two, and used another band of aluminum to tie the two halves back together, but with the inlet and outlet rotated appropriately for my geometry.

I also filled the heat muff with stainless steel wool. This should slow the air velocity down and also improve heat transfer surface area. The end result should be hotter more effective winter time heat in the cockpit.