Okay, I've been following this thread for a while. Great work. I'm sure I'm not the only one that's thrown a few of the NPI cams out that maybe I shouldn't have. Have a few questions though. Are those two pi cams mustang cams ? Truck? 4.6/5.4? Lots to think about. Were Windsor mustang cams ground special for the 99-00 cars, or were they truck cams for those years? Did bullit mustangs get the same cams as the other Romeo built pi cars? Are 5.4 pi cams the same as 4.6 ones? I see you've already got the exploder covered.
About the lifters. Again, most of us thought they were all basically the same. Do the lifters have basically the same depth/ installed height that they're not going to be a fitment issue? I.e. will a pi lifter in an NPI head stay wide open and keep a valve off the seat on the base circle? And how much difference at the valve does changing the lifters make? It's not changing the cam, but it might as well be. I don't think it will change much at .050, but it may change the advertised duration quite a bit. Don't know how hard that is to check without a way to keep the oil pressure up to keep the lifters from collapsing.
Keep in mind, the mustang may have been the last car to get a 4.6, but it was the first to get a 5spd with one. All the other car lines were limited in the EEC for the torque converter ballooning issue to 5250rpms, save mustang and the police interceptors I believe. Mustang was the first higher revving car. Perhaps the lifters were revised to handle the higher rpms, or alternately they found so much energy being used compressing both the lifter and the stiff NPI spring that they stiffened the lifter and weakened the spring tension to lessen the parasitic losses and gain mileage/ power. The installed spring heights varied also as I recall. Might have even used the same springs, just machined the pockets lower. I know the pre-f5ae heads were lift limited by coil bind, and the later ones were less so. If you had a pre96 modular, the offset retainers were needed for the larger cams.
