The PI Head Swap...

[red281gt]

1 "The Car"
IMO the PI heads/intake is the only thing that seperated us from the newer mustangs.  And We have better looks!!!
Also, the charseis has been relatively the same since the fox body until the 04 GT.
So all these guys that say "the 96-98 is the worst ever!!!....... you should just buy a different car." bla bla bla.
If that's they're opinion, they're welcome to it - but I prefer to look at the whole picture.


Here's a basic rule I consider when looking at upgrading parts.
If the new part doesn't remove a resitriction in your engines air-flow, you will gain no power.

The PI heads are a big restriction if you want more power - ie. more air-flow.
they have decient low end and some torque to get you going, but at about 4800 rpm they fall on they're face.
BC, the airflow is maxed!

To increase power on these cars there are a number of bolt on's avaliable.
I have done most of them and only recommend gears, CAI, and Exhaust (mufflers)
Gears- you really feel the difference,
CAI- is relatively inexpensive, and you can feel a little difference, though some brands are crap.
Exhaust- it's all about the sound, minor power gain. 
hedders are cool, but dont give you much, if any power unless you add a blower.  KB doesn't even recommend them for they're kits.

Most bolt-on's dont give you much of a power gain to be worth the cost, I say save it for a blower or, in our case
PI "stuff" and/or blower.



II. " The PI"
So, on the PI note -
There's basically 3 options to gain power...

1a- PI intake swap without adaptor kit - gains 18 rwhp NA. (naturally asperated)

To do this, you will need the following parts:
XW7Z-9439-AA intake gskt $6.08 ea
F8AZ-10153-EA alt brkt $10.53
XR3Z-18B402-AA coolant tube $19.67
F1VY-8255-A thermstat housing o-ring $3.83
F1VY-8507-A water pump o-ring $2.43
XR3Z-9L437-BA upper plenum o-ring $3.05
F75Z-8555-AA coolant tube nipple $5.73

1b- PI intake swap with adaptor kit - couldnt find dyno results but I'm sure it's a little more power because there's no
step inside the runner where it meets the head - resistance.
Livernois has a kit with the adapter plates and all the parts, or you can just get the intake.


2- PI intake and custom cams -
You can get a decient power gain from this, there are a few different cams for NPI heads, NA or supercharged.
You're looking at around 40 HP gain here.
VTengines.com has some good cams for this.
but remember - this is the limit you can gain, your increasing the volume of air the cylinder can take by using the cam,
gaining a little extra flow with the intake, but are limited by the size of the intake ports, and valve stroke.


3- The PI Swap - consisting of the PI heads and intake, and all the gaskets, head changing kit ect.

Gains 60 HP straight swap.

Gain - 100-120 rwhp (supercharged - meaning on a car that was alread supercharged, not the heads and blower gains added together)

Gains 80-130 rwhp ported with cams, naturally asperated.

Ported Heads, Intake, cams and  blowers... all you could use. 
A guy at THP I spoke to got 780 rwhp with ported PI, cams, forged bottom, and turbos.
and alot of tuning...    all out of his "crappy" little 2V.

Other examples:
I can't find the link, but on corral there is a long thread I was involved in, a guy on there was in the same boat, my cousin is in - had a vortec wanted more power, did the PI headswap, kept same boost, all that - gained 110 rwhp.
So supercharged, he gained over 100 HP by only changeing the heads and intake.  He did no porting or cams. (that I remeber)
That's impressive.

As I mentioned in other posts, I've talked to a number of guys that got 130+ rwhp with ported PI's, custom cam, and a good tune.
This also leaves you potention to increase power in the future if you want more.


Let's not forget that the mighty 5.0 is a 2 V. with 1 cam, and can get awsome power.  Are there different heads avaliable for that?...


III. "The Rest"
Once you get here you have to look at the rest of the drivetrain.
Our rods are limited at approximately 450 rwhp - after that your chances of sneezing one out of the block are good.
Forged rods, pistons and Crank are recommended.
After that your transmission will blow up, and axles can go if you push over 500 rwhp.

Another thing I see is people say the compression will go up......
So what.   the modular loves high compression.  and if you're adding a blower, that's what your doing anyway.

If you go custom cam or porting you will need a tune.  I recommend finding a very experieced tuner.  It makes a big difference.
Detonation is the main cause of a blown engine.
the main cause for detonation is a bad tune.



Money is the big factor with the Swap.
Until reciently it was about $3000 or more depending on what you wanted in way of porting, valves and cams.
The labor involved can also add up if you're paying someone to do it.


1350 for everything,  WOW.
1595 at powerheads.


As some have stated, you can find used PI heads, for even less.

So, to sum it up:
If you want between 250-350 hp, a blower and bolt on's will do you.
(Or the PI swap and good cams.)

If you want more than 400 - the PI is a must.
It's the place to start for serious HP gains.

Best wishes to all, and don't underestimate the potential of our cars!

Article from sn95forums.com

[rick focks]

good thread... i got a set of clean pi heads with cams for $300... there's deals to be had

[MustangChris]

rick.. youre such a whore.

[jthorn9]

Good post up, I have a buddy that wants to buy a 96-98 GT (tried to talk him into a Cobra for the extra 2Vs, but he won't listen), but it's good to have the model numbers for the gaskets and what not, because he's going to give me the money for the parts and I'm going to order them and install them, and I really wasn't looking forward towards looking for a specific part number for a 4.6L. It was already pain enough doing the work in my 5.0 lol.

[rick focks]

rick.. youre such a whore.

thanks buddy!!

[MustangChris]

Good post up, I have a buddy that wants to buy a 96-98 GT (tried to talk him into a Cobra for the extra 2Vs, but he won't listen), but it's good to have the model numbers for the gaskets and what not, because he's going to give me the money for the parts and I'm going to order them and install them, and I really wasn't looking forward towards looking for a specific part number for a 4.6L. It was already pain enough doing the work in my 5.0 lol.

your friend is wise... i dont want a cobra...  .. .only a termy...

for a street/strip car making 500 HP, a 2v is the way to go....  you'll have to re-build the motor on a cobra and a 2v for 500 HP, but when it comes to the head work, the 2v is half the price...

[MustangChris]

thanks buddy!!

lol, np man ;-)

[droptoppony]

Whats a PI?

[Powder94]

Power Improvement

[droptoppony]

So it gets more power? how and how much power?

[red281gt]

you can get around a 65 rwhp gain.

[jthorn9]

Well I wouldn't say 65..............

NPI 96-97 Mustang GT 4.6L - 215 bhp
NPI 98 Mustang GT 4.6L - 225 bhp (I personally call BS on this one, 96-98 GT dynos all look about the same)
PI 99-04 Mustang GT 4.6L - 260 bhp

[SilverStang03]

good write up, idk about the better looks, but yes the heads are all that separates my motor from a 96 to 98. those heads alone add like 50 hp, and imo is one of the best mods you can do to make the car faster.