P&P NPI Heads or Swap to PI Heads

Ok, here's the plan for my car in the upcoming months. I'm definitely going up to 9-9.5 pounds of boost and adding water/meth injection. My goal is to have 380-390 rwhp on a very conservative tune. Because I've seen a lot of guys on the Thundercoupe and Supercoupe forums making 30-40 rwhp less than this with the same setup as me, I've decided to go a step further to ensure I meet my goals.

While cams would probably provide a nice gain, I've ruled them out because I don't want any loss in fuel mileage, and I want to keep the car as subtle as possible. This leads me to heads.

Choice A.) Buy a set of PI heads and send the blower off to Steigemeier for a port and polish (including port-matching the runners to PI head specs). This would up the compression to a level that I don't feel particularly comfortable with, although my tuner is assuring me that it would be perfectly fine with the use of the methanol injection, and that I'd easily reach my goal this way.

Choice B.) Port my NPI heads. I'd also at least upgrade to PI valves, or maybe something else if someone knowledgeable about the subject thinks I'd benefit from a larger valve. It would be optimal if the ported NPI head flowed the same or slightly better than a stock PI head; that way, I wouldn't have the higher compression problem that I'd have with the PI heads.

Both options cost roughly the same, so I'm planning on going with whichever one will get me to (or close to) my goals all-the-while being as safe as possible.

Nick at MHS, if you see this, I'd love for you to chime in with your opinions. If I go with Option B, I'll almost definitely send them to you. I'd like to see the flow numbers on your NPI heads, as well as what kind of gains you think I'd see with my setup. I'd also like to know if you think it would be worth it to upgrade to larger valves.


What says Stangnet?

Ah! You guys stop tempting me with the cams! Haha. And I should mention that I do already have PI cams. I forgot that that wasn't in my sig.

Dark04GT said:

Cams make you lose gas mileage only if your right foot gets heavy. I recently averaged 27mpg on a long highway trip w/ my cams.... that being said I would include cams with what ever head modifications. I think a good set of mild blower cams from MHS would really complement your blower and get you towards you goal in no time.

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Yea, after doing some reading around, and some logical thinking, it looks like I'd get the gains I'm looking for with a set of decent blower cams (and half the cost). I'd guess that I'd be around 360 rwhp with 9 pounds of boost and water/meth; so I'd only be looking for no more than 40 horsepower extra (which I've heard is easy to get with cams from my current setup).

The main thing I'm worried about is the install. Definitely don't want to end up with any bent valves...

ItsStock02 said:

The bump of compression will definitely help you out with your power goal. That being said I say swap to the PI heads and add PI cams. If e85 is available around you switch to that as well, it will help out with the higher compression.

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Yea, no doubt that the PI heads would get me there. If this was a track car or a weekend-only car, that's probably what I'd do. I just don't feel comfortable running that compression and boost in a daily driven car (that is regularly driven "spiritedly"...)

98COBRA281 said:

do i even have to tell you what i think????

port the NPI's. throw some SS swirl polished valves in them, with a good valve job, good springs. i have $500 in my heads including resurfacing, valve job, springs. valves, seals, everything!

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Yea, I'm almost definitely going to stay NPI, even if I don't port them. Would be sweet to have a stock block, stock NPI headed car in the 11s.

You like your MHS cams?

fast97gt said:

no no no no no do not swap to pi heads when your goin FI. you DO NOT want a high compression motor with any type of FI. also there not many options for aftermarket cams when you do the swap. PnP your npi heads (checkout 98cobras stuff very nice) go with a blower cam. (cushmen motorsports has some nice ones, along with crower.) ive seen charts that if done right that ported npi heads flow way better then pi heads and could flow as much as 4v heads.

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Well, regularly I'd agree that you don't want to mix the boost and compression. BUT, with my setup, I'd be running methanol injection, which ups the octane quite a bit and allow to run both together. I still don't feel 100% comfortable with that idea, but my tuner said that lots of people have been doing that lately because it makes such good power.

Flghtmstr1 said:

You should just give Nick a call. He's very helpful, and trustworthy to a fault (he refunded $10 to me that I wouldn't have even missed).

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That's the plan.

N8Dogg98 said:

Will I have no mechanical background and installed my cams using Nick's write up. It's definitely not something a novice wrench should attempt, but if you know your way around your car and your toolbox you'll have no problem installing them yourself.

I also have a set of MHS cams and I absolutely love them. I'm kinda pissed that I went to get a tune w/o reinstalling my CAI and new spark plugs. I laid down 237 RWHP with just the cams, UDP's, a PI intake, PP plenum, catted x-pipe and a MAC cat back. Since the tune I reinstalled my CAI again (had removed it for a while cause I thought about selling it) and changed plugs and it feels like I gained at least 10 more HP and extended the peak torque by at least a couple hundred RPM. I'm planning on going back to the tuner soon to see if there was a difference.

Long story short, get the cams... you won't regret it. Like 98COBRA281 I love my cams!!!

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Yea, I wrote that before I read through all the articles on his website. I definitely feel more than competent for the job. I mean, I installed the PI cams, cat back, mid-pipe, suspension, blower, and tons of other odds and ends by myself, so I don't think I'd have a problem with it. My main concern is all the specialty tools that I'd have to get to properly degree them.

So let me get this straight: If I use his cam degree service, all I have to do is mark the timing chains (which with over 100,000 miles, I will definitely be replacing), and then match up the marks on both gears? Is that it? If so, I don't feel like this will be difficult at all.

And yea, I'm DEFINITELY leaning towards the cams. I haven't heard any actual numbers from his particular NPI blower cams, but I've heard numbers ranging anywhere from 30 rwhp and 70 rwhp with other 2 valve blower cams out there. I'd be very happy with a nice 30 horsepower bump. That plus a little more boost and water/meth should put me very close to 400 rwhp.

AND, I don't know how they will sound, but his Stage 1 PI blower cams....http://www.youtube.com/watch?v=k_Fom2QWgsE...:drool: I could probably sit around and listen to my car for hours if it sounded like that.

Flghtmstr1 said:

If you're using a factory-thickness head gasket, you should be okay, but I'd call him to be sure. I have to fully degree my cams despite the degreeing service because I'm using a thicker head gasket.

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I'm not planning on touching the heads, so I'll still be on the stock gasket.

N8Dogg98 said:

Here's the problem, according to Nick only 1 set out of 50 cam gear sets are in time themselves. So what he did for me was write the intake centerline on each cam (he assembled the cams and the cam gears). For my car it was 113* on the drivers side and 110* on the passenger side. Then I used TFS adjustable crank gears to acount for the difference. I had to advance the passenger side 4* and the drivers side 7*, but the TFS gears go in increments of 2* so my car is off by 1* bank to bank, which Nick says is NBD.



Dude I'm sure the blower cams are different, but my stage 2 NPI cams sound SICK! I'll have to take a video and post it up here one day.

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Ok, so unless I'm the lucky 1 in 50, I'll have to buy the Trickflow crank gears? If so, Nick is giving a helluva deal! $200 for the crank gears AND degree service? Nice!

N8Dogg98 said:

Will, I also replaced the chains, tensioners, and guides when installing new cams. May as well do it right the first time (nice)

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Yea, that's the plan. I've seen lots of old threads with people talking about losing motors due to a broken timing chain. No need to not spend the extra few bucks and do it while I have everything apart.