If you are using the jacks to undo the head nuts you must back
the jack off a full turn, pump the jacks up to pressure and you
should then be able to back the nut off less than 1 full turn. If
the nut is brought up to a stop against the jack and tension is
released it will bind.
On tightening down you can screw the jack down onto the nut
without backing off, as when you tension you turn the nut down and
away from the jack.