To increase the amount of hot surface area in the heat muff, I used an ordinary screen door spring. It was about 18 inches long when I bought it. I put one end in the vise and stretched it out to about 12 feet. I then spiraled it around a piece of one inch o.d. pipe. I heated it with my propane torch until the shiny galvanized coating turned gray. That removed the temper from the spring. It was then very easy to wrap around the exhaust pipe. I secured it at each end with stainless steel wire.
My heat muffs are tear drop shaped in cross section. I joined the small edge with piano hinge. The heater hose to the carburetor attaches to one end. The reason for making the muff easily removable is that it must be removed for inspection, since it would be a most dangerous place for cracks to occur. I have pictures if anyone would be interested. Jim Vance va...@hbcomm.net
