I am assuming you mean cabin heat. When you open up the cowling, look at the back of the aft baffling (The sheet metal that extends to the upper cowl behind the cylinders. That is where the air that passes through the exhaust heater muff is obtained. It goes through a hole in the baffling, through a (usually orange) piece of SCAT hose, and into the muff. Another piece of SCAT takes the warmed air to the heat box on the lower firewall.
I don't know why, but the heated air comes through the firewall into the space under the floorboards. Fat lot of good it does there. If you don't have one already, you need a register in the front floorboard to direct it into your part of the cockpit. I believe there is a photo at ercoupe.info in the interiors section. Greg
