When I torqued my head on my '92 300E I seem to remember that you should wait in between the initial torque to 70nm and each 90 degree cycle. I did not replace the head bolts. But, I did make sure they were well lubricated with motor oil. The last cycle of 90 degree turns was interesting. You actually could feel the head bolts stretch. Also, you work from the center of the head out. There should be instructions included with the head gasket.