Liquid cooling

[LarryK]

Since I have a Liquid cooled motor I am installing a fan and heater core in the cabin, just like a car, would there still be a need to have an outside air source/air vent? How sealed up is the plane in flight? Typical/general of course.. are there any good ways to get fresh air into the cabin without cutting into the side of the airplane for scoops or inlets?