>  I have the smaller 1988 cast iron manifold,
>and including pipe, my total exhaust weight is 12 pounds.  What appeals

>me most is that it is compact, simple, and I don't have to worry about

>walled pipes glowing red inside my cowling, as the cast iron manifold
>absorbs a lot of heat that would otherwise turn exhaust pipes red hot.

         The noise reduction with thick headers is real. Thin headers on
cars make a noticeable increase in the noise level. They make a lot of
high-pitched "ping-hiss" sort of noise. (At the instant you first
disconnect an air tool, it makes this sort of sound.) It is like you can
hear the valves opening through the thin-wall header pipes. The pipe

also rings with each exhaust pulse.

         A thick-walled pipe only delays the temperature rise and spreads
out any hot spots. It does not reduce the final, steady-state, average
surface temperature. The thin-wall pipe will indeed have more prominent

spots. These hot spots will appear on the outside radius of the bends as
they leave the engine, where you can see them easily.

         It is probably be a good idea to use thick-walled pipe for the
first several inches, and then transition to thin-walled pipe. I don't
know, but I suspect that the stock manifold is quite a bit thicker than it
needs to be, however.


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