There's been much discussion over this. It was believed that all '03 and all '04 Cobras had 4 threads from the factory, and that only the latest heads (01/05) had 9 threads. New information indicates that all 2003 Cobra have 4 threads, early '04 Cobras have 4 threads, and '04 Cobras built after some date in 11/03 have 9 threads. However, even these revised '04 heads don't have the revised coolant passages found on the heads released in 01/2005. This is interesting information because there have been reports of spark plugs blowing out of the heads possibly in part due to the lack of sufficient threads and possibly also due in part to an improper installation of the plugs. I don't believe there is any substantial proof that 4 threads is a potential issue since the reported cases of blown out plugs is so few, but obviously having 9 threads is better than 4. I find it interesting that Ford changed the number of threads at some point in the 2004 production run. The question is why they would do that if they weren't concerned about the heads only having 4 threads.
