Brief Description: Cabin Heat Muff Installation - Part 1
Since it can get pretty cold at altitude, its pretty important to have an active heat source in an airplane. Unlike a car, where heat from the water jacket is used, in an airplane, a special heat muff is attached to one of the exhaust pipes. Air from the outside is forced into one side of the heat muff over the hot exhaust pipe, and then routed around the engine to a control valve mounted to the firewall. This valve allows the amount of hot air to be controlled from the cockpit. Unused hot air is vented into the cowling compartment to keep the pressure through the heat muff system constant.
The Vetterman 4-into-4 exhaust system came with a two-line heat muff designed specifically to fit the exhaust system and the contour of the RV-8 cowling. Assembly was fairly straightforward, but it seemed like the long threaded rods were a little bit too short for the length of the muff chamber and it was a real pain to finally get the washers and nuts on. The muff also didn't exactly fit tightly around the exhaust pipe, and the manual suggestion of drilling the screw rod holes to #28 so that the clamps could be tighten more, helped a little, but not that much. I finally found that I could shove the muff all the way up toward the cylinder where the curve started and was able to get a fairly tight fit that way. I added another stainless steel hose clamp on the opposite side of the muff right on the exhaust pipe to make sure the muff didn't slide back down again.
