4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

Non-PI vs PI

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Old 06-12-2006, 06:28 PM
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Red3
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Default Non-PI vs PI

What is the difference between these two engines? I am about to have my 3.8 swapped out for a 4.6 out of a '97 I think maybe it was a 98. I know I won't be making much more hp but I will have the sound. How hard is it to get a non-pi to perform? Is there really any big setbacks to this motor?
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Old 06-12-2006, 06:31 PM
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redass02gt
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Default RE: Non-PI vs PI

pi stand for "retarded flowing cylinder heads" and npi stand for "even more retarded flowing cylinder heads". the diff is about 45 hp.
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Old 06-12-2006, 06:32 PM
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2000GT4.6
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Default RE: Non-PI vs PI


ORIGINAL: Red3

What is the difference between these two engines? I am about to have my 3.8 swapped out for a 4.6 out of a '97 I think maybe it was a 98. I know I won't be making much more hp but I will have the sound. How hard is it to get a non-pi to perform? Is there really any big setbacks to this motor?
The NPI heads are terrible, the cam is weaker, and the intake is more restrictive. You can expect around 210 to 220 RWHP from full boltons and this motor. They are very weak factory stock, and they do not respond well to mods.

A PI headed engine you can expect 260-270 WHP from boltons. They respond much better to mods and have better stock componets. Also, there is a much larger aftermarket for these parts.
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Old 06-12-2006, 06:34 PM
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jmmorgan82
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Default RE: Non-PI vs PI

if your gonna have it swapped and the motor is gonna be out of your car, probably on a stand...why not swap the heads for some pi heads and put some nice cams in. You'd really appreciate the power and it would be alot cheaper than doing it down the road.
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Old 06-12-2006, 06:58 PM
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Red3
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Default RE: Non-PI vs PI

So if I have to swap my motor anyways would it be worth it to go to the NPI motor or back to the 3.8?? I might be able to get a motor out of a 2000 but he isn't sure if he has the computer and all the wring harnesses I would need for that engine but he knows he has it for the NPI. What do yall think I should do.
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Old 06-12-2006, 07:03 PM
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amoosenamedhank
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Default RE: Non-PI vs PI

Really don't waste your time with a npi engine. All that work you won't be happy with what you end up with.
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Old 06-12-2006, 07:04 PM
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mightyb28
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Default RE: Non-PI vs PI

Call the auto salvage yards and find a cobra. 2001+ cobras and do it right. Better not to waste time or $$$ on a sub par engine.
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Old 06-12-2006, 07:16 PM
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Red3
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Default RE: Non-PI vs PI

Well, I don't even have the money right now to be able to afford the swap. The mechanic that is doing it is letting me pay him x amount every paycheck. So you think I should get the guy to see if he has the stuff I need for the PI motor?? It's out of a Saleen did Saleen do anything to the engine when they built their cars?
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Old 06-12-2006, 07:55 PM
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2VNA
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Default RE: Non-PI vs PI

I would 1 like stated above get a pi engen or a cobra to put in, the one your talking about won't give you what your looking for. Lets fact it. GT's are pigs stock and need help.
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Old 06-12-2006, 08:00 PM
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Morbid Intentions
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Default RE: Non-PI vs PI

yea... do 99-04's have NPI or did the NPI's only come in the earlier 4.6's?
that's one thing I'm left in the dark on
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