Torque of the head bolts.

[valyidol]

In front of me is the HUMMER H1 with the 6.5 diesel after rebuild. The mechanic who did the build was lost. The owner asks me to check the head bolts are tightened corectly or not? I have no imagination, how can I do it? Does anyone know what tightening torque will be after 90 и turning ?
Someone told me that in the old manuals the last tightening of the bolts was not in the 90 turn. "

 

[Will L.]

Sorry, can’t do it. Buy new head bolts and head gaskets. Both are one time use. The head bolts are “tourqe to yield”. That’s why you go to measureable spec then 90 degrees more. That extra 90 degrees is literally stretching the bolt out of shape on purpose. So they can never be reused again. Once stretced they will not torque properly and will break.

Once that happens they are done. Talk to the other mechanic and if he admits he only tightened to a certain exact amount that is lower than specifications AND the engine has not been started you could finish specificaton torque. If it was started even for one second- drive it how it is or take the heads back off and start over.

This is advantage of head studs instead of using the head bolts. They can be loosened and retightend. If engine ran with them loose, head gasket could still have been damaged, but a slight better chance since re- torqueing is possible.
Or buying only gaskets and reuse the studs as many times as you wish.

http://www.thetruckstop.us/forum/threads/torque-specs.612/

Copy from above thread:
Cylinder Head:
1988-1995:

• First--20 (25)
• Second--50 (68)
• Last--1/4 Turn or 90* More

1996-1998:

• First--20 (25)
• Second--55 (75)
• Last--1/4 Turn or 90* More

 

[6.2 turbo]

Start at 100 ft lbs ,and work your way up to 120 ,in 5lb increments. You might have to stop before 120,if a couple feel soft.

 

[valyidol]

[QUOTE = "6.2 turbo, post: 558944, участник: 5159"] Начните со 100 фут фунтов, и проработайте свой путь до 120 с шагом 5 фунтов. Возможно, вам придется остановиться до 120, если пара чувствует себя мягко. [/ QUOTE]
Thank you