an old trick i've heard from the british car folks might work ...

remove the spark plug and turn the crankshaft pulley until one of the
pistons (on the cylinder head you want to remove) is at its lower
point. then start feeding small rope or cord into the spark plug hole.
stuff as much as you can in there. then turn the crank pulley one more
complete turn and the piston will push against the rope and the rope
pushes against the cylinder head and off she comes.

joel