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Message: <blockquote data-quote="Silver95bird" data-source="post: 1404336" data-attributes="member: 21743">5.4l heads different?Okay, I hope nobody minds me joining in the conversation here. I joined this forum directly to reply to this thread, it's that good. I got searching into 5.4L things because I'm going to be acquiring a 5.4L engine soon (for free), so I'm learning as much as I can about them. The engine has F75E heads with "5.4L" stamped into them (NPI). I knew that there were revisions in NPI heads, such that some things like high-lift cams won't go into the older F1AE/F4AE heads as easily as the F5AE's, but I kind of assumed development basically stopped there. Since there are at least 2-3 different NPI Windsor heads, how many/ which ones have the more open exhaust ports? Has anyone flowed a set of these different castings? It's kind of hard to tell from some of the pictures, but how much more open are we talking? One of the long standing NPI/PI relationships was that the intake/exhaust flow ratio was a little better for NA from the NPI heads, and the PI heads were a little more favorable for supercharging. Is that now in question? Then there's the whole what happens if we try 5.4L heads on a 4.6L, and vice versa. Oh, and if this isn't enough, let's ask those questions all over again once we start porting the heads. I know it's a lot to throw out on a first post, but this got me curious.Are we having fun yet?</blockquote>