Why Do you Back-off to Torque ?

[marc hildebrant]

Group,

I have just replaced the head gasket on the Model A. As such, I have been told to re-torque the head bolts after a short time, and then later after 500 miles.

The instructions from the garage was to re-torque, by first backing off 1/8 turn, and then torque to 55 lbs. per foot.

I have been doing this, but why do you first back-off the nut some ? Why not just re-torque to the value directly ?

I re-torque the head cold.

Marc