PI swap or just cams?

With a catted midpipe, catback, PI intake, 3.73's, MHS stage 2 NPI N/A cams, stock plenum and throttle body, and stock intake tube I made 237 RWHP and 281 RWTQ on a Dyno Dynamics dyno.

I've since installed an o/r h-pipe and a CAI, so these numbers may be a little higher now. FWIW, my car would likely put down around 265 RWHP on a dynojet as Dyno Dynamics tend to read 10% lower than Dynojets.

With a PI head swap you're looking at around 270 RWHP (on a Dynojet), but you'll lose some low end torque w/o the advantage of being able to run a more aggressive intake centerline cam with NPI heads. NPI heads offer much greater PTV clearance and this allows you to run an aggressive intake profile.

NPI heads + cams typically provide 15 lb/ft more torque in the lower RPM's than a PI swapped car. However, the PI swapped car will continue to pull all the way to 6000 RPM's and will give you 5-10 more RWHP (notice how quickly the power falls when my car gets above 5200 RPM on the graph below).

If it were me, I wouldn't do a PI swap unless you were installing ported or TFS heads and some aggressive cams. It's a fairly involved and expensive process to swap heads, while cams can be installed fairly easily. It took me all day one day to install cams in my car and I replaced all of the timing components while I was in there.

Post up your results when you're done. I'd highly recommend cams from Modular Headshop. Nick McKinney owns the shop and he's a great guy who knows a lot about the modular 2V engines, specifically the NPI cars. He also offers a service to degree the cams before shipping them. It's only $150 and highly worth it as most don't have the necessary tools to properly degree cams themselves.

All in all it cost me $750 for the cams and degree service, and an additional $50 for an adjustable crank gear. The PI intake was $200 new from Summit Racing, and the other misc parts necessary to do the intake and cam swap probably cost between $200 and $300.

You can decide whether or not to replace all of the timing components (guides, tensioners, timing chains, etc...). I figured with 140K miles I may as well do it right if i was going to be in there.

The PI intake is easy to swap as well. Using the PI intake gasket is easier than using the NPI gasket, and I'd recommend you buy a package of new o-rings for your injectors from NAPA before doing the swap. When I re-installed my fuel rails they tore into my old worn out o-rings and when I tried to start the car gasoline was pouring everywhere out from the cracks/tears in the o-rings between the injectors and the fuel rails. I'm lucky it didn't start on fire and burn the garage down.

Or Option 3: swap in a complete PI motor.

So long as you have a decent place to do it and some patience, it's actually quite easy to do. I found a 30k mile PI motor from a Grand Marquis for $600 out the door. I wouldn't say that's too bad. And it's pretty darn straightforward as well.

Also, pulling the heads is VERY simple once you have all the cam components out. The mechanically-inclined first timer will probably take 14-18 hours on a complete cam swap (chains, tensioners, and all), or at least that's about how long it took me the first time (second time was less than half that, haha). Swapping heads will take <2 hours on top of that. So I wouldn't say that it's a lot more involved than a cam swap.

Oh, and regardless of what some people's opinions are, remember that "PI" stands for "Performance Improved". Ford didn't spend all that R&D money and put those PI motors in the Mustangs for no reason. Dollar for dollar, PI >>>>> NPI. Been there, done that.

Agreed Will, a PI engine would be ideal, I didn't suggest it as the OP only asked about cams +intake or PI head swap. Pulling 2V heads with the engine in the car is a PITA.

I would recommend a PI head install over a complete PI engine. The PI heads on a NPI engine will get your compression ratio to around 10.5:1, which will certainly help. Most who have done the swap say they are fine running mid-grade.

Cost wise, you can do a pi swap from the jy for around 300 bux with headgaskets, most of the time you just clean the heads and intake and they are perfect. For another 2-300 you can put a teksid shortblock in the car, including gaskets, new main and rod bearings and rings, you might have $800 into it, and it is a SOLID 280whp car with out any kind of big bolt ons, like lt's or cams. You need to run it off of 93 but damn is it worth it. basically would make the power of a mach 1 or n/a C head cobra as well.

here's how it works, the Pi intake is the biggest gain of the pi swap. The cams offer up around 15hp, and the heads themselves do flow much better, however it really feels like around 20-25hp for just the heads.

The lazy mans pi swap consists of just the cams and the intake. That alone is almost a 40rwhp diff. A full pi swap car with some bolt ons (mainly an o/r x pipe) will do around 260rwhp.

N8Dogg98 said:

Agreed Will, a PI engine would be ideal, I didn't suggest it as the OP only asked about cams +intake or PI head swap. Pulling 2V heads with the engine in the car is a PITA.

Click to expand...

I gotcha. I suppose I was just making sure ALL of the options were on the table.

Lemme sum up my opinion.

REALLY small budget and easy to do: PI cams/intake. Can easily be done for <$300 and is worth a solid 30 rwhp. (P.S., I've got TWO extra sets of PI cams laying around. )

Much better gains in power: PI head swap or PI motor swap. Just the head swap if you want the most power or don't ever have plans for boost. The entire motor if you may want boost one day or don't want to have to put 93 octane fuel in.

At the VERY bottom of my list would be an aftermarket NPI cam swap (no offense N8, I've done it, too ) I've done a cam swap and a PI motor swap, and all said and done, the PI motor swap was significantly cheaper, and netted a MUCH larger power gain.


I've said this in previous threads, and I'll say it again. I've been in the NPI Mustang game for right at 6 years now, modding for about 4 (all on the same car). Knowing what I know now, and if I had to do it all over again, a complete PI motor would be the very FIRST mod I did on the car. Simple, cheap, non-complicated, and you don't even have to go into the motor to do it. PI heads alone are a great option if you know that you don't ever want boost, but they WILL be a downfall if you ever decide to go boosted.