Would someone clarify for me, exactly what years had the blowout problem. When did it start, and when did Ford add more threads to the heads?

Thanks

 

97 - 03 - Both V8 Modulars had 4 thread plug chambers, any of these could have that problem. Very easy to cross thread.

Sometime in 03 the 2 valve head plug chambers were modified with more threads . I'm not sure how many threads were added or what casting numbers these heads have, but I believe Ford is still using them in the 2 valves. Their also the most problem free modular head design Ford has.