I'm routing the exhaust tubes from custom mufflers on my MVVS 26 gasser powered 1/5 scale OV10 Bronco through the nacelles to exit at the scale location on the outside of the nacelles. Part of the outer 7/8" SS tube is exposed inside the nacelle with all the engine ignition and throttle servo electronics. I'm running a 3/4" exhaust tube inside the 7/8" tube for isolation of the heat. I was hoping that the airspace between the 7/8" tube and the 3/4" exhuast tube would be enough to reduce the heat inside the nacelle.

Can anyone tell me the approximate temp. of the exhaust and is there anything you guys would recommend to insulated the exposed tube inside the nacelle. The outer tube is a tight fit through the balsa and ply construction but I could increase the hole to allow for some form of insulation. I have some woven fiberglass sleeves that are good for up to 1000 F but they don't insulate much.