Here's my 2 cents.
When my mechanic pulled the head on the Bavaria 2 years ago (marginal head
gasket, the head itself was dead straight and not cracked) we went around a
bit because he felt the best course was to rebuild the '73 head. I
respectfully questioned his sanity, knowing he has worked on my Bav first at
the dealership then at his own shop for close to 20 years.
Then, as I was ready to drive away, I asked when to return for a retorque
appointment. His reply, the factory trainers in the mid to late '80 started
recommending the angle method on all BMW engines including the M30 sixes.
The change in technique had more to do with the construction of the head
gasket than the bolts, but he hasn't had them return since he started using
that method close to 15 years ago, and he's pulled and rebuilt heads on lots
of BMW engines.
I know it sounds crazy, but he said keep it cool and sleep well at night. So
far, so good.
Caveat: The only preventative measure is keeping the engine cool. If I had
an original M30 engine with head untouched out of the factory, I would not
mess with the head bolts in any way.
----- Original Message -----
Sent: Wednesday, January 23, 2002 7:04 AM
Subject: Retorque of Head Bolts??
> There is a thread on the www.bimmer.org messageboard about retorquing
> cylinder head bolts. Nobody there seems to know the answer yet. I recall
> hearing talk and tips about this awhile ago myself. Is there a
> maintenance procedure for higher mileage BMW 6-cyl engines to reduce the
> chances of a blown head gasket?
> Which engines use torx headbolts (per Bentley manual, need to be angle
> torqued twice after a regular pre-torque), which use regular hexhead
> says pre-torque, torque again after rest, and retorque after engine
> warmed-up), and which use allen head? Which is better?
> I am guessing that the torx bolts stretch and can't be re-used where as
> standard hex head bolts can? I'm guessing that Allen head bolts are high
> performance application? If it ain't broke, don't fix it?