Why do the OEM head bolts always get kicked around?Rajunz said:A bolt is made to stretch a given amount, this is where it gets it's clamping force. To do a metal head gasket properly it needs to be torqued 75-80 ft. lbs. The stock head bolts were not designed for this value.....
I torqued my OEM head bolts at 72 ft/lbs on HK$ MHG ~70K miles ago, & the engine still runs like gangbusters."The metals used in the head bolts of the 7M & 2JZ engines are identical in
metallurgy +/- manufacturing S.P.C. This is a good material, it stretches
smoothly in the plastic region of the curve before it snaps."
"My calculations show that the 7M head bolts when torqued to the factory
specifications of 52 to 58 ft. lbs. is in very low tension related to the
bolts actual yield curve. Calculations based on my test data show torque
values for the 7M head bolt could be as high as 68 ft. lbs.s to 82 ft. lbs.
without putting the bolt into the plastic region."