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Re: Head Gaskets

To: rick@rbmotorsports.com (Rick Byrnes), land-speed@autox.team.net
Subject: Re: Head Gaskets
From: ardunbill@webtv.net
Date: Wed, 14 Mar 2001 19:31:39 -0500 (EST)
Rick, thanks for those thoughts, I wish you would delve more deeply into
this subject because the integrity of cylinder head joints, especially
on high performance equipment, seems not to be a settled matter.

"Torque to yield" seems like a curious concept, could you elaborate?  On
the surface it sounds like you are torquing a fastener until it gets to
the stretch point, and a little more will break it.  How does an
aluminum head fit into this scenario, with all the casting expansion?
What kind of head bolts are we talking about?  Grade 8 bolts or ??  Who
establishes the yield point for the fastener? 

I noted in the factory Service Manual Lincoln says if the cylinder head
of my all-aluminum Mark VIII V-8 is removed, all the head bolts must be
replaced with new.  One use and they're through.  Must have been
"torqued to yield".   Sounds expensive.  The cylinder head joint of this
high performance V-8 is a minor miracle to me anyhow, it has to have an
infinite service life with NO oil, coolant or compression leaks, whether
in the tropics or the arctic.  40 below zero in Minnesota to 110 in the
shade in Florida.  All that aluminum block and aluminum heads expanding
and contracting with every stinkin' degree of temperature change.  Not
to mention the combustion chamber pressures (a lot there too, it's a
heckuva engine).  

So please tell us more.  Regards,  Ardun Bill

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