Well, I'd say run, don't walk from the 2003 6.0, it took them a while to sort it out. The 7.3 never did get sorted out, the cause of cackle and knock was the way Ford dead-ended the fuel rails without any way for air to return to the tank, it stayed in the rails until it went through an injector. The Navistar 444 had a pressure accumulator on the fuel rail, and excess fuel went through the rails in the heads and back to the tank.
I thought the real problem was 'water hammer' due to the opening and closing of the injectors from a solid metal fuel chamber. Standing pressure waves and all that crap, no place for it to go. #7 and #8 fire adjacently from the same bank, the waves from #7 had not dampened by the time #8 had to fire. For awhile Ford played with a special #8 injector. Really poor design IMHO. Ford's better idea I guess, and not Navistar's fault. The 6.0 was plagued by fuel injectors that leaked fuel down into the crankcase. Lots of fuel, resulting in oil dilution and engine damage. -- Jim
