[s-cars] Re: Valve Job Anyone?

Mihnea Cotet mik at info.fundp.ac.be
Thu Jan 15 17:40:08 EST 2004

Kirby, lol, I didn't mean to flame anyone using ARP studs...

Now I've never bought airplane insurance either.... in more than 30 flights....

Mihnea, thinking about airplane insurane in Belgium, C.

At 17:33 15/01/2004 -0500, Kirby Smith wrote:
>Since I'm home with a cold and temporarily awake, but too dumb to know
>better, I'll throw my 1787 USA half-cent into the fray.
>I find it unlikely that an Audi supervisor would approve use of a very
>expensive (to Audi) steel type for the head studs, thereby cutting into
>Audi's profit.  I'd bet that Audi would find another way, such as using
>more studs.  Thus, the Audi stud steel could easily be of a lower
>tensile strength than ARP studs.  However, lower doesn't automatically
>mean inappropriate.  There may be more than enough strength.
>Why not get some steel of the appropriate thickness, drill the proper
>clearance hole, torque up an ARP stud and measure the stretch.  Then do
>it for an Audi stud.  Is there a significant difference in stretch?
>And at what torque does each start to fail having passed its strain
>limit.  If the ARP studs prove to be stronger, then question is, is the
>tensile strength of the Audi studs times their sectional areas greater
>than the forces being applied to them?  What if it is the head that
>deflects under cylinder pressure, not the studs?  Certainly the head
>will try to squirm around.  The studs are clamping aluminum, I presume,
>so some metal flow is possible, potentially reducing clamping force.
>These factors could mitigate the value of greater stength studs.
>On the other hand, even if the Audi studs were strong enough I wouldn't
>flame someone for buying ARP studs any more than I would flame someone
>for buying airplane insurance, even though probability theory suggests
>that they are wasting money.
>Mihnea Cotet wrote:
> >
> > Heck, I'll throw my 0.02 Euros in here too then :-) and don't forget that
> > right now 2 Eurocents is worth more than 2 murkin' cents :-))))
> >
> > I am fully with Scott on this one. ARP studs are useful if you're having
> > permanent head gasket issues, i.e. you have to swap the head gasket every
> > few months, even once a year. AFAIK and IME, this has never been a problem
> > for anyone running a 20vt engine, unless that person would have used the
> > stock, NLA paper head gasket every time.
> >
> > So, really, what's the advantage in having studs over stock stretch bolts
> > in a high performance engine? If the bolts are torqued properly, they will
> > never be a problem by themselves. ARP studs are more expensive (I think 3
> > times more expensive but I might be wrong) than stock bolts and if you
> > don't replace at least 3 head gaskets over the lifetime of your engine,
> > they aren't worth the expense. So if it's a matter of having "ARP head
> > studs" written in an extensive signature line describing all mods, then I
> > agree, it's "better" to have ARP studs than stock stretch bolts.
> >
> > Now if you're having head gasket issues on a 20vt motor, the problem is
> > elsewhere and it has to be found and solved and ARP studs won't be an
> > advantage at all over the stock bolts.
> >
> > Mihnea, bolting heads up in Belgium and not knowing nuttin' 'bout dynos and
> > studs, C.
> >
> > <succeeding flack snipped but available from the archives>

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