Head bolt torque? Theory/ history / legend/ fact?

[carl johansson]

OK guys, I know that the 7MG-E calls for 58 ft lbs in a 3 step progression. I know many insist that number is wron g, that a mistake was made in the original literature, and the bolts should be torques to 76 or so foot lbs. (working off memory, but I think those numbers are correct, or at least close).

I have a pretty savy well respected engine builder with all the equipment and 30 years of experience, wins in evey kind of racing you can imagine in his engines, and did alot of work for toyota for 10 years.

He rebuilt my 7-MG-E. when I asked about the torque, he said he had never heard of such a thing, and that torque was typically based on the diameter of the bolts, and the head bolts on the 7MG-E are ment to be torques right around 55 - 60 lbs, which puts it in the original number. Too much torque will pull on threads in block and could pull it out.

so - what is fact? what is fiction? what is the history, and when did this amping up the head torque come about?