You and some others here are somehow confused about how a VW heating system works. They did not capture warm air from the cylinder fins; they captured heat from the exhaust system. Maybe this photo will jog your memory?
If you were smelling something bad it likely had a crack in the tube that channeled exhaust through the center of the assembly and carbon monoxide was getting into your cabin. Most general aviation airplanes have a similar system that has an enclosure that goes over the muffler.
Those heat exchangers always worked great as long as they had no holes in the heat hoses and the cables and levers were in good working order.
Simple maintenance.
Darn good car though. Would start in bitter subzero cold.
Wow, I learned to drive a stick on that car around 1966. It was our second family car (first time Dad had ever bought a second car).
All these years I’ve been under the impression the heat came from the air blown over the cylinder fins! Thanks for setting me straight on that. Nothing like over 50 years of misapprehension!
I drove that bug onto a shallow frozen pond and heard the ice starting to crack! Luckily I was able to get off before it fell in. Stupid teenager!