And just to clarify people, it's usually a PRODUCTION related problem, not a design flaw. In the course of manufacturing a cylinder head, there are many many processes and a ton of machinework involved. You get one guy or one piece of renegade machinery, on one shift, that gets out of spec... or you get raw materials put into process that are out of spec, or any 50 friggin thousand other scenarios, you can wind up with a run, or scattered instances, of defects. Ever hear of a casting defect in a block or crankshaft?? Poop happens sometimes, in fact, it happens all the time in manufacturing. You just never hear about it if the company has good countermeasures in place to check for anything that "falls through the cracks" in their process sheets. The fact that Ford found this themselves is a sign of a proactive company, not a "build now test later" scenario.