NON-PI head porting

invertmast · Jan 3, 2006

Ok,
I've got a 96 GT w/ the SVO supercharger. I've also got a set of complete 97GT cylinder heads back home just sitting there collecting dust. I've read (thru doing some searching on here) that supposedly the non-pi heads flow more in the higher lift cam selection than the PI heads. I don't have the $$ for a set of PI heads and a new SVO blower to go with them, sooo.. Will i get any gain from having the non-pi heads P&P'd? I also plan on going with a set of larger valves and some Comp Cam 270AH cams or a set of VT stage 2 cams.

Thx,
thomas

TGJ · Jan 3, 2006

Well to run those higher lift cams, you are going to need the Crower Offset retainers and either Comp or Crower springs. To use the VT Stg II cams, you are going to either have the heads spring pockets machined or notch the pistons.

Depends on who does the NPI heads. If they are done properly, you will see a very good gain.

invertmast · Jan 3, 2006

I'm planning on getting a Mild Street Blower cam to go with the supercharger... I might not go with those 2 cams exactly, but i'd like to get a good 20hp increase w/ the cam addition, and a decent lope.. nothing too crazy

I'm also thinking of gettin steenracing.com to do the head porting.

Gearbanger 101 · Jan 3, 2006

Personally, I'd just go with a set of stock PI cams and add the PI valve train to a set of ported NPI heads. The SVO blower doesn't move enough air efficiently to really make the most of a set of aftermarket cams. Unless you plan on building up some sort of custom water/methanol cooling system, you’re not going to be able to run much more than 7-8psi (even with a really conservative tune), before that blower starts sending ACT’s out of control. Not to mention that in adding more aggressive cams, you may find yourself with a substantial loss in low end torque, with very little gain in horsepower. Most off the shelf blower cams are meant to be used with Centrifugal chargers and won’t work well with your set up or Positive Displacement blowers in general.

Spend the money you save on the cams on a couple more intake and exhaust mods instead, like a larger Throttle Body and/or better Mass Air Meter or Cat-back. You'll benefit more from them.

billfisher · Jan 3, 2006

wait dude. i got my pi's for 300 dollars. complete. covers,cams,heads low milage. do it.

Gearbanger 101 · Jan 3, 2006

billfisher said:
wait dude. i got my pi's for 300 dollars. complete. covers,cams,heads low milage. do it.

With the FRPP blower being of the non-intercooled variety, he's going to have a tough enough time keeping ACT's at bay without the 10.4:1 compression ratio a PI head swap is going to bring when combined with his shallow dish NPI pistons. For his purposes, porting the NPI's is the best method.

46gtsblown · Jan 3, 2006

I would recommend getting the blower ported to increase its effiency, Magnum Powers do this service.
I would also suggest the Comp Cams XE 268H.
With the offset retainers as suggested in an earlier post.
With this cam you will not have any problems and still have a good gain.

Dwayne

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