sc400 torque head bolts and then turn 90 Degree???

[Davek]

Hello,
I have a 1997 sc400 and i was told to torque the head bolts at 29 lbs and then turn them 90 Degrees??? Is that true?? I've never heard of that. I would think you torque to specs and that's it! please help, because i want to get it right.
Dave

 

[XR8tt]

Yep that how [TTY] "torque to yield" head bolts are done..
So it doesn't matter if thread is slightly tighter than another ..
They should all pull up the same..

Some use 30Lb 60* and 60* from centre out..
Which I used on 13mm studs..

 

[stevechumo]

That's standard on many cars. Actually, 25-29 lbs for the first time, then 90 degree, then another 90 degree. If you only turn 1 time for 90 degree, it won't hold. This method is to use with engine oil.

 

[Zuffen]

Be aware they are basically a one use bolt.

They stretch on use and shouldn't be re-used.

The workshop manual has some specifications where if the bolt is thinner than a specified dimension it should be replaced.

Best practice would be replace them with ARP studs as it won't cost you any more money but they at least reusable.

You can get stud sets from this Site.