Results - modified PI intake on NPI heads

[91LX2Bfast]

I have tried explaining to some members on here that the PI heads are not all they are cracked up to be. Sure they are worth some HP, but I tried to maintain that a lot of the gains have come from the cams and intake manifold. Well, here's a little something to help my cause: PI intake on NPI heads

[Hammer]

I'm glad it was worth 15-17 rwhp...

But it doesn't change the fact that the heads are the bottleneck on 96-98 stangs.

Not the intake, not the cams...

15-17 rwhp compared to 30-40 rwhp with nice flowing heads alone.

If you are strapped for cash and do your own work, a modified PI intake\PI cam may be worth the cash\time, but if you're serious about getting the pony to run, there is no replacement for better flowing heads....

Add a blower to both combinations and you'll definately be able to tell the difference.

[91LX2Bfast]

Hammer - not that I doubt your experience, but I have to disagree with your specific statement.
If you put PI heads w/ NPI cams and a NPI intake on a stock 96-98 bottom end you will not get 30-40HP....Its not happening. In fact, I'd say that 80% of whatever increase you get will be from the increased compression ratio.
I know that this dyno is skewed because of the ported heads, but once he dyno's the PI cams and PI intake on a stock 96-98 block, we'll see where the gains come from. And you'll have to remember about the CR on the 96-98 swapped cars.
IMHO, the heads themselves are not the power maker that everyone thought they were.

[Hammer]

If you put PI heads w/ NPI cams and a NPI intake on a stock 96-98 bottom end you will not get 30-40HP

I used to have a dyno sheet that proved otherwise (when using the motorsport heads), and I even had the stock cams... I wish I knew where the heck it was... (Probably sold it with the car)

Replacing the heads and intake was worth a best of 45 rwhp (depending on the dyno run) on an NA setup... admittedly other mods such as the Pro-M MAF, shorty headers, full exhaust and a kickin' custom tune helped matters...

this is a case where previous mods, if well thought out, will add to the gain of later changes as the whole setup benefits...

In fact, I'd say that 80% of whatever increase you get will be from the increased compression ratio.

With the PI heads you could be right, but with the motorsport pieces, you don't have a CR issue. Plus you have a better base for a forced induction setup.

I know that this dyno is skewed because of the ported heads, but once he dyno's the PI cams and PI intake on a stock 96-98 block, we'll see where the gains come from. And you'll have to remember about the CR on the 96-98 swapped cars.

Its also skewed because of the modified intake...

Any engine work when well thought out will make increased horsepower, and to be honest, I'm not a HUGE fan of stock PI heads either. But in case you haven't looked at the flow rates on the stock 96-98 heads, they are downright anemic....

To be honest, I really wish after-market suppliers would give 96-98 owners more of a choice other than PI or motorsport heads if they are looking at upgrading their heads.

I have a buddy up at Dallas Mustang that took a set of PI heads and ported them with a ported bullit intake. He showed me the flow #s from that set of heads... It was absolutely amazing...

You can play with cams and compression ratios all you want, but airflow through the engine is a key to power (if managed correctly)... and its only as good as it's weakest link.

[surfbeast]

2BFast,

I get your point, The P.I. heads are better, BUT they are not "ALL THAT"! They flow better than the 96-98 heads but other things factor in also. I would put a set on my car but with the added CR and the cost per HP( 40 hp max div by $ 1,100 min = $ 27.50 per Hp at best) it aint worth it to me. Now the motor sport heads are a different thing all together, still to costly for me though. A few issues ago in MM&FF they had a stock( except cat back ) 98GT dynoed at 204 rwhp. The same issue had a 2000GT stock ( with cat back) dynoed at 216 rwhp. They put over 3K in heads and intake on the 00 gt and it's best dyno was 245 rwhp. over 3K for 30 - 40 total hp gain is prety costly to me. O yea, the 98 got a $ 700.00 nirous system and was putting down 306 rwhp! stock! ( remeber these numbers are out of my memeory so don't flame me if i'm off by a few hp ) I get the point on the P.I. heads!

[Red Mustang Gt 46]

Excuse my ignorance but I've been out of the loop for a while (working O/T for my 98 rebuild). What is a modified intake, a 99+ intake? I have a set of Comp cams (268 grinds) waiting to be installed on my 98 Romeo...I'm curious...

[96_4.6]

Yea I check here everyday and never seen this thread could someone explain it alittle bit to me cause i have a 96 gt. Now whats this about a ported intake on non PI heads meaning I saw in that mm&ff mag about the new lower intake is that what everyone is talking about cause I will never see a PI head swap hate to be an idiot here but if someones bored explain this alittle bit to me, thanks

[91LX2Bfast]

You guys have to check out the link.
KD took a PI intake, and reshaped the ports to fit the NPI ports on the head.
In his words from the link: "As for the process of how to make one of your own, see the other thread for the most part, just get some NPI gaskets, overlay them on the PI intake, scribe the outline of the NPI port size, wherever the line drops into the port makes the boundary of where the epoxy needs to go, then rough up the inside area, mix up and pour in your epoxy and let it set up good before trying to shape it with the die grinder. You'll probably have to do multiple pours in each port, in order to get it all in the right places you have to position the intake different ways to keep it from running down into the port or just running out of it. Also, I did put 2 sheet metal screws in each port from the backside so the threads were protruding out into the port where the expoxy needed to go. This gave the epoxy that much more to hold on to, and hopefully it will never come out. The screws were longer than needed and were just ground down while shaping the epoxy. This isn't a very difficult project, it just takes some time to do."
On page 2 of the link, there is a picture that shows the difference in the port cross-section size between a NPI and PI intake. Observe how much larger the PI runners are.
96_4.6 - when we were talking about your C&L upper, this is what I was trying to tell you about, the size difference between the PI and NPI intake ports.