[s-cars] Re: Valve Job Anyone?

[QSHIPQ at aol.com]

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