What is PI short for, how are PI heads different from non-PI heads, and what year did Ford change the 4.6 and 5.4 heads to PI heads.

Thanks

 

PI = Power Improved, the intake ports on the PI heads are larger and squared off while the non-PI heads are much smaller and somewhat tear-drop shaped. PI heads came on 1999 and newer F150's and 2000 and newer Super Duties. Here's a link to a picture that has non-PI heads on the left, and PI heads on the right:

https://www.ford-trucks.com/user_gal...=68793&width=0

Here's a pic of my PI heads and the PI logo between the passenger side cylinders 1 & 2:

https://www.ford-trucks.com/user_gal...=62312&width=0

 

Thanks, that clears it up perfectly.