how to remove a really tight head bolt

i tried to take off the head, and i got all of them but 1 head bolt loose. i broke 4 sockets and its not even budging. its starting to get rounded. the motor was in a accident and my friend said that i should replace the head gasket. should i keep trying to take off the head, or should i just use it. in the accident the radiator was smashed in and it slammed on the passenger side into a wall. waht are the chances that the head gasket it broken?

slim to none that the head gasket was damaged in the accident but now that you have untorqued the bolts you need to replace it. Try using a 1/2" drive impact (the black ones) socket with a 1/2" drive breaker bar, if that does not do it then get a piece of pipe and use that on the breaker bar fpor extra leverage. It should do the trick. ;)

get your friend to take it off since he told you that it was messed up, and now u surely messed it up because he probably doesn't know what the hell he's talking about.