I have an automotive technical for all you guru's out there! No, it's not a Duratech question this time so dont kill me! :p ... Anyways, I'm re-torqueing the head bolts on my 87 Supra Turbo as the torque was set *too low* from the recent head job done 5k ago. The head was milled and *new* gaskets (felpro) and head bolts (toyota) were used. The question is, should I *back off* the head bolts before torqueing? Some people say no, as you run the risk of putting to much pressure on the head and run risk of mixing coolant/oil or damaging the head gasket. Others say, it is nessicary to back off the bolts to overcome the *static friction* between the threads of the fastener and the block. Torquing the bolts without releaseing them first will give wildly inaccurate readings and some bolts *may* stay put at the orginal torque value despite the torque wrench being set at a higher torque value.
The orginal torque on the head was 62lbs. With my Craftsman *click* style torque wrench, I used factory torque pattern and set my torque wrench to 72lbs. *Without* backing off the head bolts, only *one* of the 14 bolts budged and all the others clicked indicating the torque was already 72lbs or higher. Do you think that static friction is giving the torque wrench a *false* reading? What is your opnion?
P.S. I realize the head bolts are *torque to yeild* but lab reports using the ASTM A370 tensile test show that these head bolts could be as high as 68 ft. lbs. to 72 ft. lbs. without putting the bolt into the plastic region. In short, the bolts should be fine for re-torque... or so I am told.