Outdoor wood boiler

Lol . .

Engine on the run stand there. Just for the fun of it I wonder how much heat you could make with that V8 running outside then plumb the coolant to the inside the building to a radiator with a fan on it for heating.

Burn a little gas, but oh well. If you have a 10:1 cr engine that will make heat sitting there running.

Put a pusher electric fan on the radiator and run the exhaust out of the wall. You could set a fan behind the engine also.
Maybe an exhaust fan to pull any co2 outside also.
Let the engine make the electric power for doing this.