RE: How does a gas engine act when hot?
The engine on my DR1 is actually halfway between the firewall, as I had to box it back. I added a ply plate under the inlet hole on one side to keep the air flowing past the cylinder and not dumping out the bottom of the cowl. For exit air, it can go into the fuselage and out the cockpit as the plane is mostly open. I added cooling louvers on top of the fuselage where the head is as well.
This airplane is ready to fly now, and I have had some trouble with the engine. Today, I was going to fly it, but it just stopped running and would not restart. I had fuel and spark. It was running perfectly, but I think it got hot. I was doing a lot of testing on the ground. Range test, making sure needles were set, and taxi tests. Probably ran for 15 min on ground. I could not get it restarted at the field. When I got back to shop, it fired right up.