I think that cam sucks. Try an E303 or Crane 2031, they are much better suited for the P heads. P heads don't flow much past 500 or 510 lift unless they are ported. The lift is too much on that cam. Also, its duration sucks, close to stock, maybe even worse! Plus, the P's like a cam with split duration. The 2031 is a great fit to your combo - I love my 2031. It idles pretty mean, has plenty of low end for the AOD, and pulls like a mofo clear to 6k.
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91 GT - Cobra Intake, FMS 65mm TB, C&L 73mm MAF, GT-40P heads, Crane 2031 cam, Crane 1.7rr, Built AOD, Art Carr 2400 non-lockup converter, Transgo shift kit, BBK cold air, FMS 'P' headers, Pacesetter off-road H, BBK aluminum pulleys, Flows w/dumps, FMS 4.10's, Steeda STB, StangNet LCA's, for now...
Original GT-40P Tech Page