I am about to torque my right head after a rebuild (and new head gasket/cam/followers/valve seals/) on my '85 380 SE.all the bolts are in ,but not tight.I was about to torque them,but am now confused about weather I need new head bolts or not because of "Stretching"?Everything came apart no problem,all bolts looked great I cleaned all threads and used motor oil on the threads before I installed them.Do I really need new bolts?Is the problem when I torque them ( thread damage?).Any input greatly appreciated.

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'60 190b
'77 300D
'78 240D
'82 300TD