My engine is an air cooled Jabiru 2200. It has a shroud mounted over the heads, that directs cooling air to the heads. Of course the CHT still gets to about 300, so the air flowing over the heads is warm at the back end. Which got me to thinking. I could put a hole in each shroud (right and left), add a small duct fitting each side, run the small ducts into a fitting on the firewall with a butterfly valve and lever for opening it in the cabin. It would take the unfiltered air flowing over the heads into the cabin; which ought to add some cabin heat, and may actually improve head cooling by allowing more cold air in at the front end. Comments? Suggestions? Objections? The plane has no cabin heat at all now. The carb heat muff just goes to the carb, though the duct for it actually goes in and out of the cabin. But that duct only gets hot air if the carb heat is on. If the carb heat valve were located at the carb end of the duct, I could have added cabin heat from that line.