which head for the 4.6L?

[playahata]

Originally posted by Hammer
As stang00 said, port and polished PI heads can expect around a 40 rwhp increase.

From the factory FMS heads alone will get you around 35 rwhp, add the FMS intake, and you're looking around 45-50 rwhp. These are all stock numbers from the factory, so any additional work done SHOULD give you an even better increase....

The worked over PI heads give you an extra 5-10 rwhp at peak, but the FMS heads give a better power output along the curve, lower compression ratios, and room to grow if need be.

I think your numbers may be rated a bit on the low for both heads, I gained 130rwhp with the FRPP heads+intake and a set of regrind cams and have seen PI swapped cars in the 280rwhp range. IMO a headswap is a must on any pre '99 car.

The FRPP heads outflow ported PIs straight out of the box, throw port work on top of that and they are ther best bet for performance, BUT at a much higher premium. FRPPs will cost near double the PIs new for new, unless they've come down recently.

Another good question for you would be what are your overall plans for the car? If you ever decide to go with a power adder you need to know that the PI heads will increase compression on your motor and create a very N2O happy environment, whereas if you decide to go with forced induction the FRPP heads will leave compression unchanged, a better environment for boost.