[s-cars] Re: Valve Job Anyone?

[QSHIPQ at aol.com]

Dave:
Thanks for your post.  A couple things.  First, industrial deisels are going 
to use studs more for the low volume and specific application than 
"necessarily" strength advantage.  Most industrial diesels also use a steel to steel 
mounting (many times without even a gasket), which will squirm much less than a 
cheap cast aluminum to steel mounting.  I also see two torque install values, 
one to land the stud, the other to land the nut.  Make a difference?  I don't 
know.  

Again, it's a problem vs solution.  Multiple use of a stud isn't a "solution" 
that's a convenience if anything.  A solution might be increased clamping 
force, but that's not proven (yet)on these applications (IMO):  As a problem OR 
as just a fact.  Do we even know what the comparative tensile strength is 
between the stud and the bolt?  I don't.  Do we know that increase clamping force 
is necessarily a *good* thing on a cheap aluminum head casting?

WRT hydrolocking, I've never btdt, as I'm pretty anal about threading 
procedures.  This includes proper cleaning of the threads in the block with 
compressed air.  A battery brush with rustbuster agent makes a great thread cleaning 
tool.   I've heard the stories of hydrolocking bolts many times, the good thing 
is, most folks that have "hydrolocked" a head bolt/stud have an 'n' of exactly 
1.

Industry "conventional" wisdom is ok to follow, IF we present a problem 
argument.  Since we haven't presented that at all (Hap maybe = 1) in any context or 
claim, my questions still remain unanswered.  All race teams use them, and 
all industrial diesels use them.  Ok, I am still looking for more.  I'm not 
necessarily a disbeliever, the majority of my job is to identify and correct 
problems with audi quattros.  I see neither a head bolt or stud "causing" one, in 
which case, to me it comes back to a known entity.  Replace bolt with new, call 
it a day.  If a head gasket blows, fix the problem, replace the head bolts 
with new, and call it a day.

Scott Justusson

In a message dated 1/18/2004 11:50:06 AM Central Standard Time, Djdawson2 
writes:
Not sure why you think what you think...  But let's just say that if I want 
to pull my head for any reason, I can without investing in another set of 
stretchies.

You're right... nothing but testimonial here.  But I do prefer to purchase 
things once.  In all my time of working on vehicles, I will offer that I've only 
encountered such studs on Audis and VWs.  A lot of my career was spent on 
high output industrial diesels running upwards of 40psi... on top of 22:1 
compression ratios.  Some even had turbos feeding superchargers air at 32 psi.  Those 
applications... nothing but hardened steel studs.  The explanation was that a 
stud offers the attainment of a more accurate torque value.  You are 
tightening a nut on "visible" exposed threads, with no interference.  No chance of 
gummed up threads in the block giving you a false reading, and no interference 
between the bolt shaft and the head to do the same.

One common VW failure that cost a whole lot more than a stud kit... the head 
bolt holes in the block were not relieved.  If you had residual fluid in the 
bolts hole, when you tightened the head bolts, the resulting hydraulic pressure 
could, and did, crack blocks.  Unfortunately, I've BTDT.  

IMO, why not use studs that are more in line with industry standards in heavy 
duty/high output applications?  Failed headgaskets can result from many 
things.  As you've stated, you've seen failures on cars with studs and stretch 
bolts.  No real good conclusions can be made.  However, my choice is to stick with 
industry "conventional wisdom" rather than the peculiar setup that Audi/VW 
choose to use.  It costs me nothing.
Take care,
Dave