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After putting on a new head gasket I will start an engine without coolant for 20 seconds and only 20 seconds at low idle. Then I shut it down and let the heat saturate through the head. After it saturates I will torque it and let it cool completely and then torque again.
After that I will run it again for 20 seconds and let it cool completely and re-torque.
Only running 20 seconds will not get an engine too hot and allows the head gasket to settle in without the chance of coolant sneaking in between the gasket and the head/block and causing troubles.
Works for me.