Renegade Racing has been doing this for a little bit now, and they get better intake flow numbers from the ported NPI heads then they do the ported PI heads, but on the same note they get better exhaust flow from the ported PI heads then from the ported NPI heads.
Also, you will probally make a little more power with the ported PI head then with a ported NPI head because you are getting some power from the higher compression that comes with the PI head swap.
There are ups and downs really. If you use PI heads you up your compression so it would be harder to use a supercharger with that much compression. But with NPI heads it will stay the same the compression and you can boost your 4.6 with less fear of detonation.
IMO, the renegade NPI's offer a better bang for the buck then converting to PI heads and the other parts required.
__________________
'97 T-bird LX 4.6L 2V, auto
SVO heads/intake, Vortech T-trim, front mounted intercooler, blower cams, Cobra crank, Manley H-beam rods, JE pistons, Aeromotive fuel system w/ 42# injectors, and much more
No times yet
|