The head bolts torque to 90-100 ft./lbs. so after a few years of being tightened down, they can be really difficult to turn. Use a LONG breaker bar, or maybe put a 2-foot cheater pipe over a strong 1/2" drive flex handle and use steady pressure to break the head bolts loose. I've loosened head bolts that sounded like gunshots when they finally broke free! The head studs on a 220 Cummins engine are 1" in diameter, and torque to 600 ft/lb- - - -those things are REALLY a pain in the butt to change!
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!