Paul,
What type of environment should a heat shield be designed for? How
hot can it get with a SS cover surrounding the headers? (P Port 2nd
gen with 2.85:1 PSRU) It would also need to be isolated from where
it is attached to any augmenter ducting. I found some thin silicon
reinforced sheet good for 480 F. Could that be used to isolate the
shield mount? Thanks for any help
Joe Berki
Limo EZ
Avionics almost done
I have never measured the temp in that situation as to do it
I would have to take off the cowl. That would allow it to cool.
You should use .025 SS 304 spaced about a quarter inch out from
the headers. SS has low heat transfer characteristics.
Use a blast tube to blow cool air in between the sheet and
the headers. You can use another SS sheet with some kind of high
temp insulation on the fiberglass cowl in the vicinity.
The two SS sheets should be separated by about another 1/4 inch.
Paul Lamar
Ceramic coatings keep the heat in the exhaust. If on headers or
the stock manifold, if it flakes off it just goes with the flow.
Header wrap on the outside of the heat shield would also keep the
heat inside the shield and then ducted away.
Dale Davies
Header wrap is not a good idea with a rotary. You want to cool
them pipes as much as possible.
Paul Lamar
I was suggesting to wrap the outside of the heat shield with, as you
describe, an air blast between the header and the heat shield. I know that
wrapping rotary headers is not a good idea. Years ago when Racing Beat went to
Bonneville, they had trouble with an engine not making expected speed or
power. Jim kept pronouncing the engine sound. Eventually they inspected the
exhaust which had been made from double wall tube. Trapped air between the two
tubes expanded and pushed the inner tube in and blocked the pipe. At the
exhaust temp of a rotary, the inner wall had become plastic until it cooled.
Dale Davies
-- What about ceramic coating the headers inside and out? Should save weight
and keep under the cowling much cooler and if the headers are new when coated
they will last a very long time.
Mike Ethridge
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