[V8] Retorqueing heads

[Paul Jager]

I did it on my driver's side, now will do on the passenger.
Morgan our tech went 1/8" turn. No problemo one year later.

Driving the car up a long steep hill (lots here in BC) she's smokin' like a
three drunk 'n one sober guy(s) with cheap cigars at a poker table. Even
though it's low revs I figure the chamber pressure caused the by the torque
on the engine is lifting the heads from the block, allowing the oil to
squirt out. Just a stupid theory...

Sealing/gasket technology has improved so much since that engine was built.
My Porsche 928GTS doesn't leak but the surfaces are much larger on the
engine.
The 4.2 V8 doesn't leak much volume wise, just embarrassing smoke and smell,
which is a shame. The valve seals are also a problem, if the engine is not
brought to temperature, left to sit for a day, then restarted it may not
actually start (fouled-off plugs) or will blow a plume.


PS How are the bolts heat cycled?? I am not an expert on head bolts, but..an
engine head never gets near hot enough to change the properties of steel.
The head bolts are stressed, would undergo deformation when tightened BUT I
figure the engineers would have designed them to handle a good %-age over
what they are rated for.





-----Original Message-----
From: v8-bounces at audifans.com [mailto:v8-bounces at audifans.com]On Behalf
Of Dag Bøsterud
Sent: May 16, 2008 8:14 AM
To: QSHIPQ at aol.com; V8 at audifans.com
Subject: Re: [V8] Retorqueing heads


As I've explained in my other thread (V8 leaking oil... again... and
again..), I've just replaced the head gaskets, along with about every other
gasket in the engine.

The engine was leak free for about 200-300 km, then it started to leak
again.
This is why I'm wondering how you people feel about overtorqueing the heads.
I've done this to lots of engines, but they never had stretch bolts and the
block were made out of cast iron.

/Dag
92 V8 4.2
202 000 miles - not completely leak free...
  ----- Original Message -----
  From: QSHIPQ at aol.com
  To: David.Coleman at blackrock.com ; dag.boesterud at consulgranada.net ;
V8 at audifans.com
  Sent: Friday, May 16, 2008 4:09 PM
  Subject: Re: [V8] Retorqueing heads


  I'm late too...  Here's what I'd try in the cheap sneak and pray.

  Buy a set of new head bolts.  Pull each bolt out 1 at a time, and replace
with a new one and torque to factory spec.

  Head bolts are stretch bolts, I measured a set once, they stretch
something in the hood of 5mm+ torqued.  Once heat cycled, your risk of
snapping one increases exponentially, so does the risk of ruining the head,
and/or ruining the block.  Chances are really good you need to go in and
replace the head gasket.  The *only* other way I'd consider doing this is to
do 5 hail mary's, and replace the bolts 1 at a time (start with the center
and follow the bolt replacement as you would the torque procedure) and
torque each completely to final spec, move on to the next.  Good luck....

  HTH and my .02

  Scott J
  QSHIPQ
  In a message dated 5/16/2008 8:24:25 A.M. Central Daylight Time,
David.Coleman at blackrock.com writes:
    Just out of curiosity, as I haven't been following this thread...

    Have you ever torqued down a V8 cylinder head?  The specs are massive,
and going that last factory-spec 1/4 turn as specified in the Bentley is
harrowing, to me at least.   I felt like I was either going to snap the
wrench, the bolt, or spin the whole car around.

    I guess before worrying about *over* torquing it, consider two things:

    - check to make sure it's in spec first..
    - perhaps get a new set of head bolts and replace them all, rather than
retorquing the existing ones (which are supposed to be replaced, not
reused).

    Again, I'm late to the party here, so please don't act on my two cents
alone.

    -davec


    > -----Original Message-----
    > From: v8-bounces at audifans.com [mailto:v8-bounces at audifans.com] On
Behalf Of
    > Dag Bøsterud
    > Sent: Friday, May 16, 2008 9:16 AM
    > To: V8 at audifans.com
    > Subject: [V8] Retorqueing heads
    >
    > If I were to torque the cylinder heads in my 92 V8 4.2 a bit over the
specified to
    > try and stop the ever-so-leaking right cylinder head...
    >
    > Could I try to turn the bolts 1/8 of a turn? 1/4?






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