4.6 Intake Manifolds - NPI vs. PI

edbo · Oct 12, 2005

Obviously the word is that the PI intake manifolds add substantial HP when installed onto NPI heads/block combination. With all of the problem manifolds that Ford has installed on the 96-98 4.6 motors, seems that Ford (or someone else) would create a replacement manifold available with the PI design and fitted to install right onto the NPI motor for those that are just looking to replace either the leaky manifolds or to add a little HP without having to go into replacing heads or spending excessive money for an 'installation kit'.

DropTopPony · Oct 12, 2005

if you consider a set of PI gaskets and a tube of rtv an install kit? Its pretty easy to make the PI work on the NPI head. You don't really need adapter plates or the livernois kit.

tomustang · Oct 12, 2005

^ pretty much

Arnolds97 · Oct 12, 2005

edbo said:
Obviously the word is that the PI intake manifolds add substantial HP when installed onto NPI heads/block combination. With all of the problem manifolds that Ford has installed on the 96-98 4.6 motors, seems that Ford (or someone else) would create a replacement manifold available with the PI design and fitted to install right onto the NPI motor for those that are just looking to replace either the leaky manifolds or to add a little HP without having to go into replacing heads or spending excessive money for an 'installation kit'.

Doing the swap Friday. Mine let loose last week. Bought a use 04 for 100.00 and with all the parts Tools to tap for extra heat temp sensor it will be about a 200.00 deal. Good for like 15hp. Good Bang for the Buck! You would think by now that Edelbrock, Weiand or others like BBK would do this. You have Livernois as the only kit out there to port match them. Maybe Ford has just built a very good manny and the big boys cannot find substantial gains enough to get people to buy. I mean the old day castings were horrible in comparison to the smooth plastic they use now and with Cad designing it. Look at the aftermarket catbacks for the new 05. They are not getting anything power wise better than stock just more noise.

Mel96GT · Oct 13, 2005

You should also do the PI cams since it costs under $100 to get a pair of used 2001+ PI cams on E-bay or Stangnet. I recently installed a new PI intake w/plates and some used 2003 PI cams and I couldn't be happier. The car feels like a different beast and all on 87 octane! I used the Anderson cam install tool so the cam swap was a snap. The stock tune is working well so far but I will get it dyno'd later when I finish the mods. These two mods will make a big difference on these NPI pigs (25+ hp) from 3000 to 5000+ rpms. This is some serious "bang for the buck". Compare the horsepower gains/dollar from these 2 mods to expensive bolt-ons such as al. driveshaft, pullies, or CAI. FWIW, aftermarket 4.6 SOHC performance parts are very expensive compared to 5.0 parts, so the PI route is extremely cheap.

I cannot recommend these 2 mods enough.

Joel's98GT · Oct 13, 2005

I did the PI intake and cam swaps, see sig for results.

edbo · Oct 13, 2005

Joel's98GT said:
I did the PI intake and cam swaps, see sig for results.

You are getting some pretty good results without the PI heads. What kind of tires do you use, those launch times look pretty respectable?

o0akoni0o · Oct 13, 2005

edbo said:
You are getting some pretty good results without the PI heads. What kind of tires do you use, those launch times look pretty respectable?

if you do some reading especially at modulardepot, you'll find out that the intake and cams on the npi motors is what really constricts it and npi head p&p'ed will flw very well.

DropTopPony · Oct 13, 2005

o0akoni0o said:
if you do some reading especially at modulardepot, you'll find out that the intake and cams on the npi motors is what really constricts it and npi head p&p'ed will flw very well.

if you really want good info on NPI heads and PI cams/intake check out the Tbird/Cougar forums. I've been lurking on them for years and learned alot of useful info.

billfisher · Oct 13, 2005

make sure you use pi gaskets. rtv water jacket

billfisher · Oct 13, 2005

heads flow almost the same. pi has higher C/R. i would change them just to get the extra compression. remove brows.

edbo · Oct 13, 2005

I appreciate all the info. A lot I already knew about, some I've learned a few about. I was just commenting about why Ford wouldn't just come out with a NPI fitting manifold that would fit perfectly on the NPI heads that improved HP like the PI manifolds. Now that my 'club' has acquired this braggart of an '05 owner that thinks his crap don't stink, it's time that I pull out all the stops. Can you say Cobra motor with a KB supercharger setup making over 600HP? That's what I'm talking about. Sure, a lot of dough but the baddest '98 'vert in the area! And when they think they're running a 'GT' and get their doors blown off, it'll be worth every cent!

Joel's98GT · Oct 14, 2005

edbo said:
You are getting some pretty good results without the PI heads. What kind of tires do you use, those launch times look pretty respectable?

16" bfg's about 4500-5000rpm launch

whyask · Oct 16, 2006

pi cams and intake...what HP to expect.??? (110,000 on the engine) sorry to jump the thread guys just curious

TGJ · Oct 16, 2006

whyask said:
pi cams and intake...what HP to expect.??? (110,000 on the engine) sorry to jump the thread guys just curious

25 - 30 RWHP if both mods are done.

whyask · Oct 16, 2006

sweet cams and intake her I come, Installation pretty straight forward...kinda new in the mechanic world.. Average price for an install.???

Twista · Oct 16, 2006

edbo said:
I appreciate all the info. A lot I already knew about, some I've learned a few about. I was just commenting about why Ford wouldn't just come out with a NPI fitting manifold that would fit perfectly on the NPI heads that improved HP like the PI manifolds. Now that my 'club' has acquired this braggart of an '05 owner that thinks his crap don't stink, it's time that I pull out all the stops. Can you say Cobra motor with a KB supercharger setup making over 600HP? That's what I'm talking about. Sure, a lot of dough but the baddest '98 'vert in the area! And when they think they're running a 'GT' and get their doors blown off, it'll be worth every cent!

im confused. Do you have a GT or cobra? I thought the GT's only had nonpi crap unless you own both seperate cars.

DropTopPony · Oct 17, 2006

Twista said:
im confused. Do you have a GT or cobra? I thought the GT's only had nonpi crap unless you own both seperate cars.

This thread is a year old, he probably traded in the GT for a Cobra
I remember him having a GT

4.6 Intake Manifolds - NPI vs. PI

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