PI Headswap Write-Up

Winters98GT

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When I look up these parts quite a few of them are for f150's. Put it also says 4.6l in the description but never says anything about Mustang. What's that all about?

it's all about "modular"

Parts based on a single design, so many of them are interchangable. The 4.6 was not designed for the mustang or to be a performance based motor, but as a modular design used in many vehicles.
 
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pilks

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Jul 15, 2004
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i know its ancient but the link for PI Headswap Pictures doesnt seem to work for me..... fyi
 

Fobra281

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Jun 22, 2010
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I have a Romeo block ( npi) and Im putting Windsor heads on it (pi) so which head bolts do I use? :shrug:
 

Fobra281

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Jun 22, 2010
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According to the write up you need windsor head bolts.

Part number: 3L3Z-6065-AA - (20 bolts)

Thanks Im just triple checking at this point. Because someone told me Windsor head bolts wont work with a Romeo block.
 

N8Dogg98

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Thanks Im just triple checking at this point. Because someone told me Windsor head bolts wont work with a Romeo block.

Haven't done it myself, but the write up clearly states that if you are installing windsor heads on the 96-98 stang (which is a romeo block) you need windsor headbolts.
 

Fobra281

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Jun 22, 2010
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Haven't done it myself, but the write up clearly states that if you are installing windsor heads on the 96-98 stang (which is a romeo block) you need windsor headbolts.

That was my exact statement to the person that said that to me. Im going with the write-up.;) I cant wait !!!
 

thyreaper

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Jun 11, 2011
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uhh valve cover problems

i just got a set of pi heads and i took them to the machine shop and they came back that they are from a 01-04 mustang 4.6l but i counted the valve cover bolts and i only came up with 9 on each head, my stock seems to have like 10-12 cant really see too much stuff in way, but ya the heads i got seem to only have 9 on top where the valve cover sits unless im missing one somewhere that i didnt see, whats this about?
 

thyreaper

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Jun 11, 2011
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lol no one knows? im counting the ones only on the top, are there any on the sides or anything that i dont see? i looked at some pics online and i counted 9 on those to so im sure im not counting right
 

Sunset

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Sep 25, 2011
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i just got a set of pi heads and i took them to the machine shop and they came back that they are from a 01-04 mustang 4.6l but i counted the valve cover bolts and i only came up with 9 on each head, my stock seems to have like 10-12 cant really see too much stuff in way, but ya the heads i got seem to only have 9 on top where the valve cover sits unless im missing one somewhere that i didnt see, whats this about?


1999 and and most 2000 Mustangs have Windsor based engines and 2001-2004 have Romeo based engines. Windsor had 12 bolts holding the valve covers and press fitted cam gears. The Romeo engines had 9 bolts holding the valve covers and bolt on cam gears as did the 96-98 Romeo Non-PI engines. Hope this helps.
 

5spd GT

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1999 and and most 2000 Mustangs have Windsor based engines and 2001-2004 have Romeo based engines. Windsor had 12 bolts holding the valve covers and press fitted cam gears. The Romeo engines had 9 bolts holding the valve covers and bolt on cam gears as did the 96-98 Romeo Non-PI engines. Hope this helps.

:nice:
 

5spd GT

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I went to the track a few years ago, after completing my PI Headswap and thought I would post up the results (untuned - just bolted on) from the PI Headswap.

Before with Bone Stock NPI 1998 GT (5spd - 3.27 gears - 110k):

2.356 - 60 ft.
6.332 - 330 ft.
9.647 - 1/8 ET
74.89 - 1/8 MPH
12.30 - 1000 ft. ET
85.32 - 1000 ft. MPH

After with 2002 PI Heads/Cams/Intake (5spd - 3.27 gears - 133k):

2.159 - 60 ft.
6.032 - 330 ft.
9.255 - 1/8 ET
76.98 - 1/8 MPH
11.82 - 1000 ft. ET
88.15 - 1000 ft. MPH

Difference of:

.197 - 60 ft.
.300 - 330 ft.
.392 - 1/8 ET
2.09 - 1/8 ET
4.80 - 1000 ft. ET
2.83 - 1000 ft. MPH

Same track, similar conditions, untuned. This gives a ballpark of what you can expect to gain with a NPI to PI Headswap.
 

thyreaper

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Jun 11, 2011
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the info did help, the heads i have im guessing are romeo which means i can use my valve coverfs and all... they have removable cam gears on them to so im hoping the cams are stock.... im thinking of getting some adjustable cam gears so i can advance them 5 degrees or will it not make much of a difference? and what would that be in 1/4 mile before and after? with no tune
 

Thomas Camp

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Apr 13, 2020
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I have a question if somebody can help me i have a 96 mustang gt and going by the #8 letter on the vin indicates that my engine is a windsor 4.6 but they only used romeo nonpis in the 96 gts right? Im confused hell both of my 96 gts have a windsor according to the vin