Truck Repair: curious, head gasket, gasket

Question
Are you serious? the heads actually move...can that be a possible explanation to a bad head gasket?

Answer
yes they move.if you ever take the heads off of a big or small cam cummins, look at the top of the block. if it has very many miles on it you can see the etching where the heads move.if it is bad enough the head gasket can't seal because the grooves are too deep. single head engines usually don't move around because of their size. pretty weird something that heavy bolted that tight can move isn't it? but thats what 400-600 pounds of compression can do.