While prepping for a major teardown, I'm reading the Bentley Service Manual, Cylinder Head Removal / Installation. Some of the torque settings are quite a bit different than working on an older "elephant" engine. Shortest head bolts are set at 30Nm. Then there's 3 separate stages for the other bolts, a "stage 1" setting of 15Nm (or 30, depending on the bolt size) followed by a "stage 2" setting of 90 deg, followed by a "stage 3" setting of another 90 deg.

I understand tightening them gradually, and in a given sequence, but the 90 deg stages, with no final torque reading? Good 'ol elephant engines got a gradual tightening to a given final torque setting!

As I interpret these instructions, The tightening sequence is followed using the first Nm setting for each bolt. Then stage 2 is performed by moving the wrench (not necessarily a torque wrench, this time) 90 deg for each bolt using the same sequence. Repeat for stage 3. That's it!

Is this correct? Sooooooo much to learn!

 

Yes, it's correct. Bolts that are angle torqued are called "torque to yield". It is beneficial in some certain situations, cylinder head is one of them. Makes it less likely to loosen. Downside to this is that the bolts can only be used once

http://freeasestudyguides.com/a1_4.html

 

Sounds a lot like the bolts that were commonly called "stretch bolts" --- another one-time use bolt, also used on cylinder heads.

Looks like lotsa good info in your link --- thanx.

 

As far as I know same thing just a different name.

There are also lots of bolts in the suspension that the Bentley says to replace with new even though they aren't TTY. I haven't yet but that doesn't mean it's a good idea...