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Discussion Starter · #1 ·
Hey guys

I thought i would share one of the projects ive been working on for awhile now.

Npi head porting with a cnc machine.

A little bit of background. Ive been in this modular game for a long while now, 20plus years and ive always known about the potential of the npi head. A few folks that i had followed over the years regularly hung out here at the tccoa forum such as Nick McKinney(RIP), Jonny Langton, KDanner.... they had great inspirational ideas with the npi head and wasnt secretive about their work.

Long story short, the pi head compression bump is what gains the pi head popularity. I understand that it does make sense to just swap the entire head, cam, intake package over since the intake and cam are the biggest improvements over the npi intake and cam choices. Apples to apples, both heads with same compression, pi intake and pi cam are very close to the same output. And for a naturally aspirated engine either head has great potential. The bigger exhaust valve of the pi head favors max power for the forced induced.

What most do not know about the npi head intake port is the 1st 2inches into the port is the most restricted area of the port. From there afterwards the port gets rather large. Ideally, and im no expert, any intake ports main focus is to funnel the incoming rush to the valve. And unlike 99% of any single valve head for any engine the modulars valve is not a restriction to the incoming rush. The rush slips over the valve instead of being blocked and dispersed.

Speaking of intake valve opening, the seat I.D. of a npi head is .050" bigger than the pi head.



Here with this cut a way view you can see the port floors entry squeezes tight and could use some much needed removal. And thats where the cnc machine comes in. Hand porting the opening to match a pi intake and cutting the pinched floor out for 8ports takes awhile. So what i have done is copy mapped a ground out port with the pi entry shape and wrote a program for it. The port will still need some hand blending but most of the work will be done by the cnc.



Hope you enjoy!
 

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I searched out pix like that before I started porting the C heads.
Porting i nto the water jacket is bad...
 

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Discussion Starter · #6 ·
Here is an unported npi, a cnc milled npi and a pi for comparison. I say cnc milled cause technically the port has not been ported. Only cut on by the mill. The pi has some tool mark porting but only to clean it up some for comparison.

Notice the normal npi port floor compared to the milled npi. Also notice the tool marks down into the port at where they end. Roughly 2.5" down. This is all thats has been done to this port, nothing else. No bowl grinding, nothing. I feel like by doing this, its a great start to maximizing the npi head potential.

FYI about any npi intake valve seat I.D. is .050" bigger than a pi intake valve seat I.D.




 

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Discussion Starter · #7 ·
This has always been the reason I recommend PI cam/intake swaps over full PI motor on 96-97s, Nick JL and Kdanner showed me the light as well, it’s great to see npis still getting love. I don’t think I’ve ever seen a port cutaway of a modular head before, very cool!
That cut a way pic is actually a 5.4l version npi Ford part# F7*. Ford went on to make an F8* version as well. The npi 5.4l version was the best npi head besides the svo. The 5.4l npi has big water chambers like the pi head. A thicker deck surface, a bigger exhaust port under the exhaust valve seat(port diameter remained the same tho). People claim all npi heads to be the same, but thats just not true.

Same goes for the camshafts. Its not just npi and pi cams. Its npi 4.6l panther, mustang, 5.4l truck or pi 4.6l panther, mustang, explorer, 5.4l truck. Each platform having their own particular grind camshaft. Mustang and 5.4l truck recieving the better performing cams of each head type. A simple caliper measurement of intake and exhaust lobe max lift reveals if the cam is mustang/5.4l or one one the others. The exhaust lobe will be around .030" bigger than the intake when measuring. I know the camshaft differences because i made a camshaft mapping station that measures the specs and i have like 20set of 2v cams. The explorers got the worst of the cams.
 

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That info pretty much throws a wrench into everything we've been told. Brings me a lot of questions lol.

Would you be able to post the specs on the cams, and if they had different part numbers and such?

Also the exact differences on the heads between F6/7/8? Is it just casting thickness and throat volume or are there better heads for bolt on performance as well?

Have you used a flow bench to measure how much difference the CNCing will make in a before and after test?
 

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The short side radius Could use some work, theres a sharp edge at the valve seat. That, as well as sharpening up the divider between the exhaust ports is what I did to the dohc heads.
 

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Found something on the heads.

F1, F5, F6, and F7 part numbers. All look identical except for cam caps, but we know the 96 up can hold larger cams then the previous, so obviously somethings been changed.

And sadly so many people blow these heads off that changes, either in port volume or casting thickness, probably have been unnoticed for the last 20-30 years.
 

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Found something on the heads.

F1, F5, F6, and F7 part numbers. All look identical except for cam caps, but we know the 96 up can hold larger cams then the previous, so obviously somethings been changed.

And sadly so many people blow these heads off that changes, either in port volume or casting thickness, probably have been unnoticed for the last 20-30 years.
The F1 and F4 npis aren’t anything like the F5 or newer npis, besides the valve spring seat changes that allow for more cam choices the ports don’t have that clear shot to the valve like the later npis, actually they’re more similar to PI ports when you look down them. They’re basically junk like most of the early modular stuff

Here’s where I discovered the cam variances. You liked the post, so it’s not new to you lol

 

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The F1 and F4 npis aren’t anything like the F5 or newer npis, besides the valve spring seat changes that allow for more cam choices the ports don’t have that clear shot to the valve like the later npis, actually they’re more similar to PI ports when you look down them. They’re basically junk like most of the early modular stuff

Here’s where I discovered the cam variances. You liked the post, so it’s not new to you lol



It looks the same to me
 

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Discussion Starter · #17 ·
Pi cams both passenger side
XL3F-6251-A7C
XL3E-6C255-B7B

intake/exhaust
at .006 valve lift
246*/250*
at .050 lift
200*/208*

Max lift surprisingly .480"
I always told the pi cams had .050" more lift....oh well
Lobe seperation angle 116*
 

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Discussion Starter · #18 ·
Npi cams
Both cams are driver side
F2AE-6250-AA
F65E-6250-AA(tool marking curpted any legibility. This cam did come out of a 99 crown vic) corrected

F2AE
Intake/exhaust
at .006 lift
266*/242*
at .050
210*/200*

Lobe separation angle is 113*

F65E(99 vic)
Intake/exhaust
at .006
258*/256*
at .050
210*/200*

Max lift .450 both cams
Lobe separation 116* F6 (99vic)
 

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Discussion Starter · #19 ·
F65E-6251-BA
.475" / .460" max lift
Intake / exhaust
.006" lift
272*/266*
.050" lift
224*/ 210/

32* overlap measure at the lobes

114* lsa (lobe seperation angle
 

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Discussion Starter · #20 ·
Mustsng pi cam

XL3E-6C255-BB (could be B8 or 8B. Light stamping)

Intake / Exhaust
.006" lift
244* / 260*
.050" lift
220* / 210*

.495" / .540" max lift

LSA 113*
 
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