when tightening go in a helical motion outwards (start at the two centre head bolts).
on first pass tighten to about 20 foot per pound.
on second pass go to about 45
and third pass should tighten somewhere between 55 and 62 (i am pretty sure, without looking at the green bible which is at home).
run it in to operating temperature, let it cool down completely make sure tourque settings are still ok.
run for about a week or two allowing it to get to operating temperature and cool down again numerous times, and then reverify the tourque settings again.
hope this helps, this is my method.