i tuck one of my heads off because the gasket fails or the shop i tuke it to shaved it to far,so now i found a engine at the juckyard for $300.lucky me.this is the third time i v taken that head off because of water in 3 cylinders.the gaskets are new,and i know thay rarely fail,so i ll use the head off the other engine,but win i was cleaning it.i wound rotate the cams to open the valves to check for carbon build up and found that 3 or 4 valves are loose.i can wiggle them back and fourth about 2 to 3 mm.my ?? is what in the head goes wrong for this to happen.or is it ok to leave it alone.