Re: Exhaust questions: paste, wrap, needles

[Joe Curry <Spitlist@gte.net>]

William Davies wrote:
> 
> ----- Original Message -----
> From: Joe Curry <Spitlist@gte.net>
> >
> > One large downside to exhaust wraps.  They retain heat and moisture in
> > the header and lead to premature deterioration of the header metal.  I
> > would never use them unless there was no alternative.
> 
> Joe's comments started me on something of a tangent to this thread. I was 
>wondering what bearing  exhaust wraps and coatings might have on the cracking 
>which is a perceived problem with stainless manifolds. Has anyone done any 
>kind of study on this?
>     Cheers,
>         Bill.
> 
>

Bill,
I would expect that it would exacerbate the cracking problem.  This is
because the additional heat that is kept in the header pipe makes the
metal properties change.  In mild steel headers, they tend to
crystallize and that may be the same sort of thing that happens with
stainless steel.  The process makes the metal more brittle and therefore
more prone to such cracking.

Cheers,
Joe

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