What are PI heads????????

 

HI!... "P.I" heads stand for "POWER IMPROVED". The "97" - "98" 5.4's and the "97" - "2000" 4.6's in the F-150's have a NON "P.I" cylinder head. The "99" - current 5.4's and the "2001" to current 4.6's all have "P.I" heads. The "P.I" heads have slightly larger intake/exhast valves and the intake/exhaust ports were reshaped for better flow. You have to run a 4.6 or 5.4 "P.I" designed intake manifold with these heads if you want to do a head swap to a "97" - "98" engine. Here's a few pics of the differences in intake ports between a non - "P.I" head and a "P.I" head.

https://www.f150online.com/galleries...4-794-6999.jpg
https://www.f150online.com/galleries...4-794-7046.jpg
https://www.f150online.com/galleries...4-794-7042.jpg