cryo treatment and mods to EM, dialynx in particular

Ken Keith auditude at
Thu Oct 25 11:15:06 EDT 2001

Hi all,

I'm looking into preventing warpage and cracking on a turbo exhaust 
manifold, particularly a dialynx one.

I'm thinking I could apply some of the special processes that are 
available.  What I don't want to do is trade warpage for cracking by 
hardening, or over-hardening the metal.

My idea is to have a dialynx manifold first cryo treated, then have the 
mounting flange(s) machined for flatness.  Also, perhaps machining the 
outside mounting nut surfaces for flatness as well.  

In this regard, I'm concerned with creating a sharp edge at outside 
portion of the machined nut mounting surface.  Would this increase the 
possibility of a crack developing at that point, if the manifold continued 
to try to pull away from the block?  Would I need to blend the machined 
flat area into the surrounding the metal, much like deshrouding the 
valves in a combustion chamber?  Am I asking for trouble by trying to 
machine this area flat, or is it a good idea?  I've heard that this area isn't 
cast flat and will cause the nuts to get loose or put uneven stress on the 
studs.  Here I'm asking if I should bother making it flat, and if I do, 
should I also blend the sharp edges away.

After this cryo treatment and resurfacing, I'm considering having a 
ceramic coating applied.  I'm thinking that I should do this only to the 
inside, to promote expedient flow of hot gases to the turbo.  I think an 
outside coating could be a bad thing, or only cosmetic.  I want to keep 
gas velocity high through the manifold, but not necessarily keep heat in 
the manifold itself.  I'm drawing a distinction between keeping the heat 
in the passage, as opposed to keeping it in the manifold (a thermal 
barrier applied to the outside surface of the manifold).

Those are pretty much my questions.  Also, are there any upgraded 
mounting hardware options, such as better studs and nuts?  Is it better 
to stick to stock so that they might break before pulling out threads?  I 
know people like to use stainless hardware, but isn't that softer than 
regular fasteners, and are there issues with galvanic reactions, etc?

Has anyone here had any cryo work done?  I know of the reputed 
benefits, but not of any drawbacks.  Apparently some services offer to 
do complete motors and trannys.  I guess this is done totally 
assembled rather than in parts.

Also, in the archives, someone (Scott J.?) way back mentioned that 
some people that upgrade to the two-piece manifold dont also add some 
sort of tranny support bracket, which can cause even the two-piece to 
crack.  What is this bracket?

Thanks all!


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