Anybody hand-port their NPI heads?

[Burninrock24]

These things are literally being thrown away, and I know that MHS swears that ported NPI heads outflow ported PI heads. Just wondering if anybody has ever done it. I want to do a PI swap, but want to run a higher lift cam and not have to worry about PTV issues. So even if I would port the NPI heads to PI flow specs that'd be fine. Not looking to set any flowbench records.

 

[Orange 94]

I haven't ported npi heads. But I have done a mild port of my v6. I just used a die grinder to match everything up and give it a nice smooth flow.

 

[Burninrock24]

Yeah I've done a lot of research on porting, how to do a DIY flowbench and stuff from this book: http://www.barnesandnoble.com/w/dav...ads-david-vizard/1104884132?ean=9781934709641

But I don't know what PI heads respond to specifically. I know the valves are shrouded a lot, but I don't want to mess too much with unshrouding them because it would lower the CR even more by removing material from the CC.

this book: http://www.barnesandnoble.com/w/how...ines-sean-hyland/1008517941?ean=9781613250815
gives some general guidelines to the NPI head, but also recommends adding material in certain areas which is out of my realm of capability.

 

[7.5spool]

I'd say go for it. Not many people do port them. Those 4.6 heads like it around the valve guide..behind the stem

 

[MustangChris]

never heard/seen anyone do it... would love to see it! :-D

 

[CC'S95GT]

Did you find anything on youtube.
I was able to find some stuff for my P heads.

 

[duff daddy]

The NPI heads have been ported but normally people swap them out not too long after. With the TFS and PI heads NPI heads have been dropped off the map. Id love to do an aluminum block, High compression, npi head and make people flip a *****

 

[sneaky98gt]

There's a guy on Stangnet from Florida, 98cobra281 if I remember correctly (or some variation of that), that ported his NPIs. Ported NPIs, stage 3 MHS cams, aftermarket intake manifold, full exhaust, gears, slicks and skinnies. Ran high 11s. A while back, he threw a turbo on it and was in the mid-high 10 range with enough MPH to go a good bit faster, but I haven't heard from him in a while, so I'm not sure what he's up to now.

 

[duff daddy]

He was on here for a while too, I dont remember his name but there was an npi car that ran that.

 

[MustangChris]

what kind of flow numbers do the NPIs have? is there much to "gain" from porting? I'm not familiar with their design at all outside of seeing the port shape during a few teardowns.. ..

 

[duff daddy]

you can port the fuuck out of them, but you can also end up with a little more lift and duration in the cam choice over a pi top end swap due to the extra clearance.

 

[MustangChris]

interesting... from what i understand the teardrop shaped port doesnt allow a very ideal mixture of A/F which prompted ford to advance the PI design to better allow a more functional swirling effect..... is any of that true, or just internet rubbish?

 

[LilRoush]

I know a couple of guys who ported instead of swapping and had good sucess. I wish more SVO/Roush heads had been made prior to the PI introduction. Those things out flow home ported NPI heads all day.

I think that the NPI head swap happend and became the 'thing' to do - so people stopped looking for other options. The real restritive part of the 96-98 2V cars is the intake manifold, not the heads.

 

[MustangChris]

interesting...


are there any NPI intake manifolds out there?

 

[sneaky98gt]

While ported NPIs can flow decent numbers, they still don't make the same power. I'm not knowledgeable enough to say if it's the lack of velocity, or flow numbers at lower lift, or poor port shape design, but how many REALLY fast NPIs have you ever seen? I've seen one, the one I mentioned earlier in this thread. And it was only 11.90s NA, and mid 10s FI; that car was pretty much a max effort car, too (fully ported heads, stage 3 cams, Edlebrock intake, E85, 7500 rpm, etc.). PI head cars have gone 10s NA, and will run close to mid 10s FI on stock heads AND cams.

My old setup was NPI heads, blower cams, and the blower at about 7 pounds of boost. It trapped a best of 112 mph. After a piston decided to take a crap, my entire setup was swapped over to a PI motor. Same blower, same cams, same everything. It trapped over 118 on several occasions. A 6 mph difference. My point: I agree that the stock NPI intake and stock NPI cams are big restrictions, but the fact remains that the NPI heads don't make the same power as the PI heads. Period.

 

[sneaky98gt]

interesting...


are there any NPI intake manifolds out there?

Yup, one of these.

 

[MustangChris]

Yup, one of these.

svo blower dont count

 

[LilRoush]

Sure it does! It's the intake I use.

Not sure what we are using as a baseline to compare to, but without trying to toot my own horn - my car holds it's own with what it has. Not a slouch by any means.

 

[Wichers123]

The only npi manifold is the svo manifold I run..

 

[Burninrock24]

what kind of flow numbers do the NPIs have? is there much to "gain" from porting? I'm not familiar with their design at all outside of seeing the port shape during a few teardowns.. ..

Here are the flow numbers:

They are pretty horrible in the flow region, most of the gains are to be made in low lift scenario which comes from valve seat design. NPI is a single angle, PI is a dual angle. Also there is a lot of shrouding around the valve, but I'm afraid to mess with that because it may affect the swirling effect. But who knows.