The Chilton's manual mentions angle-tightening the head bolts. What is angle-tightening? The manual also lists in order the steps to replace the head: Step 26 - torque the head bolts; Step 27 - install new O-rings in the spark plug wells. The only problem with that is that the photo for that step shows the O-rings located on the combustion chamber side of the head. Something is not right here. Can anyone help me out?