How to tell if a 4.6 2v has PI heads or NPI heads?

must2j

must2j

Founding Member
Jun 14, 2001
174
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0
Naples FL
#1
I bought a 98 gt auto a few months ago. My bro and I were doing like 0 to 70 pulls the other night. Hes got a 08 gt manual. I was hanging right there with him to about 65ish. My auto is misshifting and we both were thinkin that a pretty much stock other than flows 98gt should be gettin spanked... I know cause I had a 01 gt and spanked them. I look at the motor and it is very clean almost like it was rebuilt or something. My question is where can I look on the head without taking vavle cover off to see if the motor has had a PI head swap? If it doesn't my brother and I are both stumpped. Ive had a few mustangs now (88 notch, 00v6, 01gt, and now 98gt) and this is the only thing I can think of?

Thanks

Jay
 

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#8
Likelyhood of it being windsor is less, if it's romeo you wont be able to tell unless you snake around to the cast numbers. Look at the intake, if it's still NPI then the heads are still NPI. On PI intakes the first crossover comes from the right like this:
Picture076.jpg


on NPI it comes from the left
 
#9
CobraRed_96_GT said:
Likelyhood of it being windsor is less, if it's romeo you wont be able to tell unless you snake around to the cast numbers. Look at the intake, if it's still NPI then the heads are still NPI. On PI intakes the first crossover comes from the right like this:
Picture076.jpg


on NPI it comes from the left
Click to expand...

Forgot about that. That is an easy way to find out. Good job!
 
#11
If it has a NPI intake, you can bet it has NPI heads. If it has a PI intake, don't count on it having PI heads, there is a lot of PI intake swapped cars out there now. It would be a safe bet though that if it has a PI intake it has PI heads. The best way to really determine which head it has is the casting number. Hell, if you looked at my NPI heads without looking at the casting number, 99% of the people would swear they were PI's...
 
#12
TGJ said:
If it has a NPI intake, you can bet it has NPI heads. If it has a PI intake, don't count on it having PI heads, there is a lot of PI intake swapped cars out there now. It would be a safe bet though that if it has a PI intake it has PI heads. The best way to really determine which head it has is the casting number. Hell, if you looked at my NPI heads without looking at the casting number, 99% of the people would swear they were PI's...
Click to expand...
right, that's a given. I'm just banking on it having NPI intake therefore an easy tell that's the heads are NPI.
 
#13
Could just have PI cams though. But if you go that far, you might as well change the head as well.


I kinda wish i owned an NPI car so i could hae had the fun project of performing a PI swap.
 
#16
OK I got some time today and looked at the motor. I checked the intake manifold and it is npi so I guess the motor is just really healthy, cause I dont see how I was hangin with my brothers 08 gt.:shrug: Thanks for the help guys. Im soon doing my auto to 5 speed swap. I'll post some pictures when I put it in. I bought a TKO 600 from promotion. I had them polish the lugs and put upgraded shift forks. I'm hoping it will be a good tranny. :nice:
 
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