928 Head Stud Stretch Explained

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09 Aug 2010 02:01 #637 by Kiln_Red
928 Head Stud Stretch Explained was created by Kiln_Red
Since I am in the middle of replacing the original head gaskets in my '84 it became natural for me to research the successes and failures others have had when doing the same work. Evidently, there is a MAJOR problem with the "revised" WSM torque procedure for cars using head studs. The WSM procedure is as follows:

Step 1: 20nm or 15ft/lb
Step 2: 90 degree turn
Step 3: 90 degree turn
Step 4: 90 degree turn

This is simply not practical as either you will probably stretch studs and/or finish with 100ft/lb or greater torque values!! This explains why so many report issues with stretching and inconsistent final torques. The correct procedure eliminates "Step 4" and requires only 2 90 degree turns to be made. Again, this only applies to cars that use studs as factory hardware rather than bolts.

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