Truth about NPI vs PI

Discussion in '96-04 - 2V Specific' started by blackfang, Jan 12, 2006.

  1. 97NYstanGT

    97NYstanGT Active Member

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    wow that was a good read
     
  2. BMAC96GT

    BMAC96GT Active Member

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    Does it matter that the square ports of a PI intake won't line up to the oval ports of NPI heads?
     
  3. Johnny Langton

    Johnny Langton Member

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    Not as much as some people would have you believe.
    JL
     
  4. 1_meanGT

    1_meanGT New Member

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    very nice thread
     
  5. locksmiths

    locksmiths New Member

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    nice post
     
  6. 5point0

    5point0 Member

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    I have a question.. I was wondering with all the PI swap info out there and guys saying that they got PI sawp parts cheap.. Is it really worth doing vs just paying alittle more and getting Aftermarket HCI.. can u really find dirt cheap PI sawp parts that work.. So far when I look for parts around my area.. they are alot of supposed to be's and hiped up junk that I would never trust running.. Can we break this down.. PI sawp Vs Aftermarket HCI.. also it would be good to factor in the parts needing machine work.. as I dont trust too many out there.. Thanks for u time.. hope I have said everything clear.. :) but just would like to know..
     
  7. 97FloridaGT

    97FloridaGT Active Member

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    Another thread I've read indicated 15-18 more HP with just an intake swap. It then indicated about the same gain from a cam swap and retaining the NPI heads. All of this documented by a dyno, of course.
     
  8. Ferocious

    Ferocious Post Whore SN95 Supporter

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    Yes, you can get PI parts for dirt cheap. I got a PI intake, PI cams, and PI heads with new valve springs and rockers for $270.
    If you want to do aftermarket HCI then $270 can get you 1 aftermarket cam. :p

    That seems about right. The heads give the smallest gain i believe. They're mainly swapped in for the extra bump in compression. Cams + intake alone should new you around 35-50 rwhp depending on application.
     
  9. FrankenStang

    FrankenStang Well-Known Member

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    PI is the budget wayy to go for shur...ported PI flow just as good if not more than any aftermarket...the cams arnt the best but the heads acn be worked, and its EASY to port these heads PROPPERLY...nothing like 60 HP for under 300 bucks...only n20will net you gains like that for that price....but honestly from experiance...doing just one pi part isnt worth it...the intake is useless without the cams to help the extra intake flow and then for the extra flow NPI heads will retrict it...so one without the other doesnt do much other than add a little throttle response and engine growl...just a PI intake alone ulle lose abit of low end but regain it in the HIGHER rpm's...
     
  10. FrankenStang

    FrankenStang Well-Known Member

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    30-50 hp from PI cams and intake alone ...i VERY much DOUBT IT...awhile back i did those 2 in combination and it shur didnt feel even 20hp faster...it just once again helped in the upper rpm band..but once i put on the heads PI ( were ported hough) wholly shit it woke up the car...woke it up so much i blew all the old shit i should replaced when doing the swap...hehe now im 32V
     
  11. Ferocious

    Ferocious Post Whore SN95 Supporter

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    30 being on a mainly stock NPI engine.

    50+ is easy achievable with some sort of blower. 97stanger on here made 370 rwph with just a PI intake/cams + a vortech s/c.
     
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  12. Leo 5.0

    Leo 5.0 Active Member

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    I know this thread is old, but I want to clarify something. If for nothing else than personal knowledge.
    But in essence, all things considered...

    Would the PI intake, NPI heads, with some NPI Cams, your typical bolt ons, and longtubes, would be close if not the same to a full PI swap minus the bolt ons and exhaust?

    My reasoning is this, since the NPIs suffer more on the exhaust side, long tubes would be especially helpful here no?
    And while the PI heads bump compression, if you take that out of the equation, then the numbers should be close no?
    So in theory, PI intake, even regular PI cams, your bolt ons, and full exhaust with a good tune, should be able to net 250-260 range, as opposed to the PI heads and the compression where 270+ seems standard for the exact same mods?

    Because I had a thought.
    Minus the heads, but adding good NPI cams, shouldn't that balance out for a bit better than stock PI figures, while keeping a lower, more boost friendly CR?
    Granted at the point of cams, you may as well do the headswap, but not everyone will want to do that.

    Sorry for reviving a dead thread, but it fits the topic and my insomnia is getting to me, so I've been up all night reading, and am curious if I am off ground.

    But I would think minus the bump for compression, 250-260 would be attainable yes?
    Seeing as many without aftermarket cams with the PI swap and not even long tubes hit around 270, I am basing this off the OP statement, and many other comments saying most of our gain from the heads is the compression bump.
    Not dismissing the PI heads, but keeping on the subject of not using them for whatever reason someone may have.

    Ok, I asked.
    Again sorry, haha reading all night makes me curious.
     
  13. DropTopPony

    DropTopPony Administrator Staff Member Admin SN95 Supporter

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    You are in the ballpark :)

    The big gains were from the PI Intake and PI cams for the most part.

    If you get the PI Intake and a nice set of NPI cams you would make some decent power. Find yourself a set of ported NPI heads and be even happier.

    The best part about finding NPI parts is the price is usually much cheaper.

    SVO Heads are the the ultimate NPI head. Match that with an SVO Intake!
    Renegade ported NPI's would be the second best to find.
    Livernois Motorsports was also doing p&p on NPI's so might be some out there.
     
  14. 96blak54

    96blak54 Legend

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    Let me get ahold of them..lol
     
  15. Leo 5.0

    Leo 5.0 Active Member

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    Hmmm
    That's interesting.
    I just figured maybe I'd been up too long.

    Glad to know I wasn't talking out of my ass.
    250 or so HP at the wheels is a good amount, add some gears and that'd be a great DD. That way one could have close to if not what 99+ make at the motor at their wheels, but could be cammed, boost friendly, and have not yanked heads.

    I appreciate that! Because all I really found was a bunch of PI is better hands down. But some are just looking to pep their rides up a bit.
    230 is fairly high on the 99+ stock rwhp range, but seems the cams and intake alone get you there.
    And the graphs I found showed the heads were close but the exhaust side was much worse than a PI head, which led me to think, longtubes may add a slightly better gain on NPI heads, but I could be wrong.

    But looking at numbers, seemed like a full bolt on car, while using NPI heads would be capable of PI engine numbers out back, which while not great in terms of HP, are still very nice for the setup.

    Before I pass this info on, am I right?
     
  16. 96blak54

    96blak54 Legend

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    Stock compression comparison both heads are comparable but the pi heads will always favor better performer all because of the smaller combustion chamber. BUT! The npi heads can be easily opened up to flow comparable and the npi heads can be ran with a nastier cam before ptv contact is an issue.
     
  17. Leo 5.0

    Leo 5.0 Active Member

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    Yeah ported NPIs show to do really well.
    I remember reading the initial post ages ago and wondering if the full PI swap it so great why would you not do it.
    Then I dug around all night and discovered even unported, with a good set of cams, and the PI intake with the usual additions, while not able to do what a stock PI or pi swapped can, it is a good alternative.

    They can do some good power, not as good as a PI swap, or a PI engine with the same mods, but good in their own right.
    250+ at the wheels isn't exactly a bad deal.
    Since my PI heads fell through, I may actually go this route, and get some numbers to further help with this thread.
    Granted more power could be had, but would appear to be a good entry level if done right.
    Decisions decisions.

    Also been digging for anything by Nick over at MHS.
    He's a 2v cam guru.
    Talking unported heads and builds capable of 280RWHP if done properly.
     
  18. 96blak54

    96blak54 Legend

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    Nick is pure genius to modulars..especially npi heads. Im pulling off 281rwhp in a 5.4l on 89octane with ported npi heads.
     
  19. Leo 5.0

    Leo 5.0 Active Member

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    Yeah, I've been doing a lot of reading what he says.
    It won't be hard to see good numbers NA while keeping the NPI heads.
    And when the motor goes, I can move on to a pi or 5.4.
    But as of now, even his recession buster cams are cheaper than regular cams, and he told me depending on how good the tune is, expect no less than 18+ over just PI cams. But that would be his bigger NA cams, but he said he would expect no less than 10 over regular PI cams with his recession busters. That would make up the difference in not having heads.
    He told me for my power goals, a solid 13 second car, maybe 12s with the right suspension and tires, but for a street machine it would be faster on install and cut some of the costs, IE headchange and other things.
    He said I may not see the HP as most PI swaps, but I will have good torque. At least around 300+ peak with a very nice curve, and the ability to walk any stock PI. A PI swapped car will get me, I won't have peak potential, but for my goals, he said it's very viable.

    He was on the phone for 30 or so minutes with me, very friendly and from what I've read and seen, knows his stuff.
    So I guess I'll do an NPI build for now and explore other options towards this engine's downfall.

    Or maybe next time go ported heads, NPI motors and parts are dirt cheap compared to any PI setups.
     
  20. canzo116

    canzo116 New Member

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    I just purchased a 98 GT and am pretty handy. Would i be able to do cams and intake on my own with no experience? I dont want to screw up my engine.