Tricky choke location

I regret the cooling the is inadequate. I can understand you wanting to retain the nice shape of the cowl but i'll give the even nicer 3W 5 mins before seizing.
To explain, take look at the cooling inlet / outlet for engine and can silencer on my Decathlon

Have to agree with Kevin I'm afraid, you have no where near enough inlet or outlet for adequate cooling.

Pete Chilver's Hurricane had much more than that and the motor overheated and stopped on the maiden.

You need to expose the whole cylinder head and when looking from the front you need to be able to see at least 20-30mm of the front of the head.

Sorry guys, I didn't explain that the front of the cylinder head is actually exposed to free air as it sticks out the bottom of the cowl. The air intakes and exits to which I referred earlier are solely for providing breathing and cooling air to the fus' interior.
Also, I have heat-proof matting which will be wrapped around the exhaust manifold at least until the divergent section of the tuned pipe. This will protect the fuel tank and electrics from direct heat radiation and hopefully the gasses will be cooling rapidly by the time they hit the belly of the pipe. I have set the pipe length for mid-range power and will be sacrificing revs for torque and a high pitch prop.

I think the general rule is outlet area > inlet area x 2. Guess the tuned pipe is going to travel well down the fus, In which case i would consider some extract vents aft the T/E.

kevinross wrote: I think the general rule is outlet area > inlet area x 2.

Me too.

In saying that my Chipmunks are about 1 to 1 with no problems although my exhaust exits immediately out of the cowl.