Tractor Repair: water in oil, head bolts, head gasket

Question
I have an International 464 diesel.  I have problems with water getting into the oil.  I have repalced the head gasket twice and each time, the problem is resolved for a while, then water starts to get into the oil again. Could the head bolts be loosening up?  When I replace the head gasket the second time some of the head bolts did not seem to be as tight as they should be-90 lbs. torque.
Thank you

Answer
 Did you send the head to a machine shop to have it checked for cracks and warpage?  Also make sure that the bolt holes in the block are clean all the way to the bottom so the threads don't bottom out.  Clean the threads with a tap if necessary and blow out the holes with air.  Check that the head bolts have not stretched.  Screw the bolts all the way into the block with the head removed and measure the distance from the top of the block to the heads of the bolts.  Measure the thickness of the head and subtract it from the bolt measurements.  The thickness of the head should be more than all of the bolt measurements.  Head bolts don't loosen up, but after installing the head they may need to be retorqued after the engine has been warmed up.