[s-cars] Re: Valve Job Anyone?

[Kirby Smith]

Yes, the "racers use them" argument is a bit specious, because racers
are often funded by such companies and have to use their product.

kirby


QSHIPQ at aol.com wrote:
> 
> Kirby:
> The below looks exactly like what I queried of ARP directly (and then Hap).
> I'm all for improvement to the machine.  A couple issues I have with ARP
> studs.  First is price.  As Minhea pointed out, they are 3 times the price of new
> audi twisted head bolts.  IMO, before I would recommend that as any type of
> insurance (price=insurance argument not withstanding), I'd want to satisfy my
> innate curiosity that a) stock head bolts/gaskets are a known problem and b) that
> ARP studs "address" that problem.  As I couldn't get the answers you posed
> directly from ARP even in the most general sense, I find the sales of them to be
> only a percieved best.
> 
> Further (sharing old vw secrets here) to your questions below, if one was to
> take an average measure of a properly torqued head bolt (installed and cycled)
> vs new, one could translate that 180 final torque to a specific torque
> number, thereby increasing the likelyhood that all stretched bolts are stretched
> equally.  Some engineering types might argue that the stetch method more
> accurate, alas the racers don't.  I'll stop short of sharing that actual number, since
> I spent years postmortem with a dial caliper myself then confirmed my number
> with a national vw race car builder (the twisted head bolts are also used on
> vw - another 16v gti share)
> 
> Although your idea that the beaners are nixing the use of studs sounds
> "typical", audi/vw has consistently improved the head bolts AND gaskets over the
> years.  I suspect this is due to the beaners allowing this deviation from norm
> since a head/gasket recall would put that department into a small group seizure.
>  Certainly comparing the 10vt headbolts and fibre gasket to the 20vt twisted
> headbolts and metal gasket would support this argument.
> 
> 20vt head gaskets/bolts are NOT a known failure item.  So much so, that it is
> not used by MTM/SMS on their GroupA S2.  That indicates to me that I'm not
> the only one that believes the audi head bolts are more than adequate to the
> task. Further shared, if head gaskets/bolts become a problem, then ARP studs
> aren't addressing the problem.  Since Hap appears to be one of the very few (if
> not lone) that even has BTDT, and by definition his car isn't running right yet,
> I might present that the "facts" aren't self evident in the 20vt context.
> 
> Just FYI Kirby, I went deeper in my queries to ARP.  Specifically looking for
> more general knowlege of the "need" for them in the 20vt.  I got no response
> to the questions:  What are the differences between the non twisted head bolt
> and twisted head bolt design, and where did those differences plot against the
> "baseline" of the ARP?  What is the boost level (nee effective compression
> ratio) where ARP will actually become insurance?  Why, if stock head bolts are
> so inferior, are we (quattro list members and quattro club membership totally a
> pretty high 'n') are we not seeing more head bolt failures in subpar built
> street cars taken to the track?  Is there any data to support that a head gasket
> failure on any non ARP equipped audi turbo motor is due to head bolts?  Any
> data to support the tensile half life of reused ARP studs vs a new factory bolt
> on multiple engine builds?
> 
> ...  And a plethora more.  You get the picture.  The response never waivered
> from the corporate line that race teams use them, and so should I.  My
> conclusion?  Like my frustrating discussions years ago with Jacobs electronics, I
> suspect a price = insurance/quality argument.  Price isn't insurance, nor is it
> necessarily insuring the problem.
> 
> I'll put for that head and block prep is more important than sinking dollars
> into fasteners.  Thoroughly cleaned block and gasket, thoroughly cleaned bolt
> threads and properly cleaned and lubed fasteners.  Make sure the head itself
> is not dripping oil as you install it onto a dry gasket (see this all the time
> - use assembly lube not oil on install).
> 
> I'm with Minhea completely, buying flight insurance based on actual failure
> is a great way to make *you* feel better.  That doesn't necessarily mean the
> guy that doesn't is not as smart, maybe just a bit wiser about the statistical
> reality.  I'd argue the same about 20vt twisted head bolts.  Specific
> exclusions to acts of god (force majeur) and terrorist acts (ok mlp time to fess up;).
> 
> My .02
> 
> Scott Justusson
> QSHIPQ Performance Tuning
> 
> In a message dated 1/15/2004 4:33:57 PM Central Standard Time,
> kirby.a.smith at verizon.net writes:
> 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.
> 
> kirby