Navi/Ford collaboration. Stock 450SD 16,000LBS, 6 sets of head gaskets, then a new motor from Ford, 8000 mile past that warranty it dropped an Injector tip, holed a piston and left me on the side of the road in western Nebraska. New (Jasper)studded motor installed lasted 9500 miles before another head gasket. Repaired under warranty. Now have a 6.7 Ford in the same type truck with 150,000 miles...
"Many factors can contribute to a blown head gasket, but it all starts with the head bolts—the type and the lack of them. Torque-to-yield head bolts are nothing new in automotive engines, but once a TTY fastener stretches beyond its yield point, it becomes permanently elongated. This translates into a loss of clamping force. The 6.0L’s design employs just four TTY head bolts per cylinder (the 7.3L utilized six per cylinder). The head bolts might measure 14mm in diameter, but there simply aren’t enough of them to contend with the cylinder pressure being created beneath them."