[old ugly]

don't drain the water.
use your 11/16 box end back off the two nuts. the shield is slotted, pull out the shield, put the nuts back on, use your 11/16 box end tighten them back up. a few lbs difference in torque is not going to make a difference.
nothing is going to happen to the head gasket. you cant even pry the heads off with a crow bar when ALL the Nuts are off.
i bet most of those heads when bolted down in the back yard never new what a torque wrench was.
ou
tom