Steve
I have one in a 1940 Ford, and it works very well. You pull the knob on the front out all the way, this heats up the ink pen spring type heater element, the gas is pulled by vacuum from the carburetor bowl to the Southwind which has a choke and a form of a gas valve of its own. Inside the heater is a five inch chamber with eight pie shaped openings in it which gives the gas forty inches of burning travel. The vacuum from the engine intake pulls the burnt gases out of the Southwind back into the cars engine and it gets burnt again and pushed out the muffler. The manual for the Southwind states that if it gets too hot in the car to push the knob on the front of the Southwind in one notch, then if it is still to hot to open some windows.