[DML] Re: Rusty Exhaust Manifold Studs

["David Teitelbaum" <jtrealty@xxxxxxxxxxx>]

Typically it is not the fastener that fails, the gasket blows out. The
fastener (the stud, nut and washers and tapped hole) fail when you try
to remove them. In general if you use heat to prepare them for removal
you can "usually" get things apart without breaking anything but on
many you will rip the aluminum threads out of the head. The "best"
combination I see is carbon steel studs with double (thin) brass nuts.
This is pretty common in marine applications and can be disassembled
easily. I use "Never-Seize" whenever I reasssemble and on the ones I
have had to take apart with it things come apart easily without heat.
Another neat product that racers use is a locking ring on the nut
after you install. Eastwood now sells such a fastener, just not in our
size. This is good because the gaskets fail eventually because from
the extreme heat and the cycling the fasteners loosen over time. After
that happens the clamping force is reduced so the gasket cannot handle
the blow-by and fails. This lock prevents the fasteners from
loosening. Another possability is to wire the nuts like on aircraft so
they can't loosen but that can be hard in confined places. On many
other make cars they just don't have exhaust manifold gaskets but
eventually they leak too much so you have to put in aftermarket
gaskets. IMHO after 20 years it is good to take things apart once in
awhile. On mechanical things that are never disassembled it gets to
the point that you wind up breaking all the fasteners when you
eventually have to take it apart. As the fleet of Deloreans age we
will see more and more of this sort of thing. Another point to make is
the longer you drive with an exhaust leak the more trouble you will
have with the fasteners and you may have to have the exhaust manifold
"planed" or ground flat so it will make good contact with the cylinder
head. I am not so sure about S/S studs. If you should ever have to
drill one out it may be harder than an ordinary steel one.
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxxxxxx, "PJ Grady" <rob@xxxx> wrote:
> Hi Bill,
> 
> Not anymore! If you want a set of HARDENED STAINLESS 7MM exhaust studs I
> have a box of them on my office floor awaiting further inspection. These
> beauties are custom made for us and are stronger than the stock
studs yet
> can still be drilled out should one ever fail. Cost will be similar
to OEM's
> because we made a lot of them. I am now researching the best nut and
washer
> combination to use with them. Any comments from the "peanut gallery":).
> Qualified suggestions would be most appreciated because I've received
> conflicting advice over the years about stainless on stainless, brass on
> stainless, steel on stainless etc.
> 
> Robert Grady
> 
> 
> -----Original Message-----
> From: content22207 [mailto:brobertson@xxxx] 
> Sent: Friday, February 13, 2004 1:06 AM
> To: dmcnews@xxxxxxxxxxxxxxx
> Subject: [DML] Re: Rusty Exhaust Manifold Studs
> 
> Stock exhaust manifold studs are M7x1 -- rather uncommon in carbon
> steel, impossible to find in stainless steel. Those same holes will
> tap extremely easily to 5/16x24 (24 TPI is almost identical to 1mm
> pitch) -- very common in stainless. Tap will thread in as easily as a
> bolt, which is useful for the studs on cylinders 1 and 4 hidden behind
> the crossmember. Replacing carbon studs with stainless steel would
> make future removal problem free. Don't forget the studs that hold the
> manifolds to the crossover pipe (M10x1.5 -- also common in stainless).
> 
> Bill Robertson
> #5939
> 
> >--- In dmcnews@xxxxxxxxxxxxxxx, "D F" <funkstuf@xxxx> wrote:
> > Just a note:
> > One problem with these things is that the studs holding the exhaust
> manifold 
> > are pretty small and often rust.  My car was purchased and started
> much like 
> > yours, with a roaring exhaust leak.
> > Anyway, the bottom line was that I had to take my heads off to get
the 
> > exhaust manifold studs out.  This is just a suggestion.  It is not a
> bad 
> > idea to replace the old studs with larger sturdier studs.  I realize
> some 
> > people won't like that idea, but, it might make them easier to get
> off next 
> > time.  That's what I did.
> > Sincereley,
> > Dale Funk
> > 4984
> > 
> > 
> [Moderator snip]
> 
> 
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