On Sun, 19 Nov 2006 21:27:26 -0600, Charlie
wrote:

John wrote:
I recently ran into another case where someone sealed exhaust gaskets
with red high temperature RTV silicon sealant. I don't know off hand
what the temperature rating is for RTV but it has to be way lower than
what the exhaust flange sees. I will say the flanges and gaskets (the
thick spirotalic no blo style) were not leaking. Am I right in
thinking the lack of leakage is due more to the gaskets working as
required than the RTV?

John Dupre'

There's a car racer racing a Mazda rotary that uses rtv with no gasket
at all on the exhaust manifold. (Rotary exhaust temps make Lyc exhaust
temps look rather cool.) He says that the actual temp of the manifold
itself at the block is actually the same as the engine block. Makes
sense, if you think about it. Of course, the Mazda is water cooled &
won't be as hot as the cyl head on an air cooled Lyc. Is red rtv rated
to ~450 degrees?

Charlie
Ultra Copper is rated for intermittent 700F.Red Hi-Temp is rated for
650F. Ultra Grey also 650F. Ultra Blue 500F.Ultra black also 650F.

The stuff DOES work well on exhaust flanges, as well asfire-box seals
on RV furnaces etc.

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