PI Head Swap

  • Sponsors (?)


bdcardinal

tree hugger
Jun 10, 2003
3,612
16
69
santa barbara, CA
a PI headswap is changing the heads on your stang which are NPI(non power improved) with a set of heads off a 99+ stang or 99+ lightning, or another car with PI)power improved heads). they have square inlet ports and slightly larger valves. the main gains are from the intake manifold that you have to change which is matched to the heads. also switching to PI heads will increase your static compression ratio becaues the chamber volume on the head is slightly lower. it is fairly easy to do if you are experienced with the mod motors. you are looking at around a 70hp increase from the swap. the heads can be purchased new for $395 a head from Sean Hyland or GEFracing, with the intake manifold also being $395. there are a few other required items for the swap, mostly coolant lines. also when you do it you HAVE to use new head bolts, because the stock ones are TTY and must be thrown away when used. and no putting on long tubes is not a PI headswap.
 

nickthegenius

Active Member
Dec 23, 2002
1,631
1
38
Elwood, IN
Josh97GT said:
can someone explaint his to me, please give a lot of detail, don't know much. Would buying some longtube BBK headers be considered a PI headswap? any help please.

Short answer: No. That would simply be adding a set of headers. The PI headswap refers to cylinder heads

96-98 4.6L Mustangs cylinder heads in their stock form do not flow very well and are part of why the '96-'98 GTs had low horsepower numbers from the factory. Starting in '99, Ford started installing what are referred to as PI (Power Improved) cylinder heads. This helped to raise the stock HP rating to 260.

So what most people do is find a good set of cylinder heads and intake from a '99-up GT and install them on their '96-'98 which will give you a great horsepower boost. There are probably more parts (gaskets and various bits and pieces) that you need, but I'm sure someone who has done the swap can give you more detail.
 

Josh97GT

New Member
Apr 8, 2004
101
0
0
So If UI'm planning on installing an enitre exhaust system, catback, h-pipe, and long headers, would I need to do the headswap before this or would it not even matter. I also saw quite a few heads available, the ford racing ones, which I'm guessing are the ones on the stock GT's now, but since I'm already changing them, can I go for something better?
 

bdcardinal

tree hugger
Jun 10, 2003
3,612
16
69
santa barbara, CA
no the ford racing ones are NOT what is on the GT now. they are SVO heads and are improved over the NPI, but they arent PI. you can do the exhaust without doing the heads. however it will be easier to do the exhaust and the heads at the same time imo. you can get the PI heads ported and polished. do you ever plan on doing a power adder?
 

Josh97GT

New Member
Apr 8, 2004
101
0
0
No I wont ever be adding a power adder. So then which heads should I get? an I don't think I'll do it at the same time because I don't have enough cash to do it all at once.
 

Rio97GT

Founding Member
Mar 31, 2002
420
0
0
Southern LA
Well as far as what you should do....get yourself some good used heads somewhere. For around $500-600, I got fully assembled heads with cams and a new intake. Then get some L/T headers and midpipe. That right there will wake up the car a lot. And if you can, put some 4.10 gears in it also. The headswap, gears, and headers will all give you a good increase in performance.
 

Rio97GT

Founding Member
Mar 31, 2002
420
0
0
Southern LA
bdcardinal said:
do the PI headswap first. it should only take a day or so if you are relatively mechanically inclined. just remember to follow all the steps, dont cut corners and you;re good.
I dont know how "inclined" you are, but if you got it done in a day, well here's to you- :nice: :nice:

If by "day or so" you meant a good full weekend, well thats about right. I knew what I was doing and also had some help, but it still took a good 2-3 days not working nonstop. You are going to have some snags and hold ups here and there, so I'd set up a weekend to do it if you wanted to do it yourself. Good luck.
 

pinski

Founding Member
Mar 17, 2002
710
0
16
North Carolina
bdcardinal said:
a PI headswap is changing the heads on your stang which are NPI(non power improved) with a set of heads off a 99+ stang or 99+ lightning, or another car with PI)power improved heads). they have square inlet ports and slightly larger valves. the main gains are from the intake manifold that you have to change which is matched to the heads. also switching to PI heads will increase your static compression ratio becaues the chamber volume on the head is slightly lower. it is fairly easy to do if you are experienced with the mod motors. you are looking at around a 70hp increase from the swap. the heads can be purchased new for $395 a head from Sean Hyland or GEFracing, with the intake manifold also being $395. there are a few other required items for the swap, mostly coolant lines. also when you do it you HAVE to use new head bolts, because the stock ones are TTY and must be thrown away when used. and no putting on long tubes is not a PI headswap.

GEFRacing had the manifold priced at $189 last time I checked...I might be picking one up this summer :D
 

Rio97GT

Founding Member
Mar 31, 2002
420
0
0
Southern LA
bdcardinal said:
well i did it in a day, however it was on a police car while at the dealership and we had the parts there. did both heads, and reused the intake. but that was with a lift and all the special tools that you need.
Yeah I guess a lift would help a little bit :D I was using jack stands in my garage...but most of the work was on top of the engine anyway. :shrug: I did have airtools though so that was a big help.
 

Josh97GT

New Member
Apr 8, 2004
101
0
0
umm back on topic, I only need to know if I HAVE to do the heads first, and which kind I should buy, I rather buy something better than the current GT's since I'm already spending the cash, and I don't plan on isntalling myself anyways guys, so need to how long it takes.
 

bdcardinal

tree hugger
Jun 10, 2003
3,612
16
69
santa barbara, CA
personally i would install the heads first, you dont have to do the heads before the exhasut but i would do them first, assuming i would only do one at a time. just go with the normal PI heads either used or new from any 99+GT. they are all teh same across the board so there no difference if you get heads off a lightning, econoline, f150, or 01+ crown vic/panther applications. i would say that a competent shop should take no more than 3 days given that nothing goes wrong and they have all necessary hardware, that is assuming that you do a dyno tune after installing the heads. if you save the money and get a set of used heads you could consider having them ported and polished, that will give you some better gains over using stock PI heads. there arent any aftermarket heads out on the market today. all the ones you would buy from SHM, VT, Livernois, and others, im sorry for forgetting your names, are ported and polished stock heads. also, when you do the heads, it would be a good time to get a set of cams. everything will be apart and it would just be one extra step to the instillation instead of starting a different job later down the line.