teej281

Hey all,
Trying to help a friend out(who may chime in sometime) about what to do with his NPI car. Its a 97 Aztek Gold car. Nice car and looks great! He is wanting to do something with the motor and has been looking into doing a PI swap lately. He was kind of dreading it because he is the one doing the work and with the time he has to invest in the project it would be down for a couple weeks at least. Thats when I suggested that he look into possibly keeping the NPI heads and just doing a PI intake swap and some NPI-grind MHS cams. I've been reading that the weak points on the NPI motors arent necessarily the heads, but the cams and intake. So if he addresses those 2 elements and keeps the heads intact, he should make some decent gains.

So what are some thoughts about doing this? Am I way off my block? What do you all think?

Also, the valvesprings in the NPI heads are better than the PI heads so you can run higher rpm and more cam with them.

mrtstang

Now is your buddy basically looking to do the most minimal work possible? If so i would think leaving the heads alone might be best with just the PI intake and MHS cams.

Jay-rod427

Where is the option for a 4V? PI setup as a whole is marginal gains for the work required. Hours of work and $$$ for maybe 30hp? Find a used Centri blower non I/C 6psi and get a way better return than PI parts for prob less money.


Only since you asked for opinions. In mine that would be a waste of resources.

teej281

6psi non i/c'd on a stock NPI car would net maybe 300-310rwhp. Cams, PI intake, new injectors, and a new maf shouldnt cost more than $1200 and will net him pretty decent power numbers. I mean if he wanted to he could pay more than $800 more and get a supercharger, but not in the cards right now I dont think.

And MRT, yea. He is wanting the least amount of work for the gains. For an NPI car I think its probably gonna rely mostly on the intake and the cams. Have to make those things up to par before real power can be made. And I think that with these mods that he would be at least at the level of full bolt-on PI cars with a stronger top end, or even better. Just my thoughts from the research I've read.

But thanks for the opinions! Keep 'em coming!

Jay-rod427

I just think with all that work and $1,200 he will be disapointed. Are injectors and MAF really needed for a mild cam and intake? Stock on an NPI are 19lb injectors right? PI motors until 03 also used the 19's, even with a mild cam upgrade injectors are not needed.

mrtstang

One advantage to the stock NPI vs stock PI heads is that he can fit larger cams in.

teej281

Wow, here all this time I thought I had 21lb injectors. lol But just confirmed that mine are 19's. Pathetic. Anyways, I'd upgrade to at least some 21lb injectors and an upgraded maf from the stock on from an NPI car. 03 cobra maf's are cheap and I happen to have 2 of them. One with housing, one without. And this isnt really a mild cam. Its pretty stout in comparison to some of the PI grinds out there. I think that with the setup with a PI manifold and the stage 2.5 cams that he'd see at least 270rwhp if not better. His mods are plenum, o/r midpip, flowmaster exhaust, and an intake I believe. There are others, but none that add performance. Might make low 190rwhp on the dyno. 70rwhp+ is a decent jump in power.

97stanger

From experience doing all that stuff back when I had my non pi setup, the PI manifold is the BEST bang for the buck. He should pick up atleast 15rwhp/15tq and a better curve just off that. Cams, eh maybe 10 more hp. I would stick with non pi heads, do the PI manifold, and honestly just save the rest of the money. Whats the point in spending $500-$600 on cams, when gains will be minimal and install will be a PITA? Agreed, with the used centri option. I vote, PI manifold, then throttle body/plenum if he doesnt already have it and full exhaust, other than that suspension/tires and save for some sort of p/a. Those non pi cars dont pick up gains worth shi*. Just for numbers sake, I had EVERY bolt on in the book (slp longtube, slp offroad x, slp catback, accufab t/b, accufab plenum, steeda udps, cai, custom tune, etc) and through an auto my car pushed out 202rwhp.....after I did the blower, I later added a PI manifold and picked up 30rwhp/41 tq. Pretty good for $180

teej281

We're not talking about full bolt-on's here. We're talking taking care of the shortcomings of the NPI motor that are the root cause for poor gains to be made. He has tb/plenum and such. No longtubes either. But I have to say, doing those cams would add a hell of a lot more than 10rwhp. If they only made that much power, do you think they would even be offered? Since the cams and intake are the biggest drawbacks, fixing those would put you ahead if you wanted to do nitrous or a blower or something. Through a manual, I think those cams and the intake would net a great gain personally.

97stanger

on stock untouched non pi heads, no...he wont pick up a lot of power with any cam in there, let alone a "hell of a lot more". And thats a pretty stupid response, why would they be offered if they didnt? Hmmm, lets look at underdrive pulleys, throttle body spacers, t/b and plenums for that matter...why are they offered if guys pick up 5rwhp for $300 per mod???

Ask me how I know. I have done all non pi swapped parts to PI swapped parts, I dont "read" what they do on the forum. I did everything first hand and for money/labor wise your friend would be best off just doing the manifold.

You have to think ahead, if hes doing a blower down the road, there will be no need for cams as his stock shortblock will be already at its max, so why spend all that $$$ and labor time to install a part to say it will help down the road on a centri car?? If he is planning on doing a centri down the road the only thing he will need to change is the manifold, PI cams have too much lift and less duration than a non pi grind and arent ideal for blower cars anyway (again, ask me how I know).