Im wanting to do that infamous PI head swap this summer. My cousin has a boneyard of 97-03 f-150's and i figure i can find a set of PI heads in the process. What else parts wise will i need to get this done. I know the usuall gaskets and what not, but actual parts that i will need since they didnt come on the truck. I guess what im asking will the PI head just go inplace of my non pi head and work all the same. Also what do you guys think a fair price would be for a set of used PI heads. Hi or Lo millage.

 

Your best bet is to just do the PI intake and cam swap. The PI headswap bumps the compression up and you will have to run premium fuel all the time. With the cam/intake swap you pick up 20-25rwhp. The PI heads will pick up another 10 or so. When in the hands of a proper machinist, the NPI heads are much better than the PI heads.

 

first off what is the NPI heads. Never heard of those. And with the cam and intake swap, do i need the throttle body to or is it the same. Also why would puttin the pi heads on bump the compression up. Dont they use the same block?

I run premium anyways because of my programer so thats not an issure really. But the flexiblity is nice.

 

PI heads have smaller combustion chambers. NPI heads came on older 4.6. In the Mustang world they were from 96-98. On f150s I beleive 97-00 but don't quote me on that..

 

NPI heads and cams are the non pi parts. The PI heads bump the compression due to their smaller combustion chambers. PI motors use pistons with a dish in the top of them to bring the compression back down. If you ever plan on going with a forced induction setup you will want the NPI heads. The throttle body and everything is the same.

 

Dont the PI heads have larger ports and what not for flow?

 

The PI heads have 49cc combustion chambers and the NPI heads have 52cc.

The PI heads also have larger valves and a smoothed out intake port as compared to the NPI heads. Most of the gains from a PI swap come from the cams and intake.

Like I said earlier, the NPI heads are better than PI if you have them ported. The head swap is not worth the money IMO for the gains. You would be better off buying a used set of NPI heads and having them ported and then doing the PI cams.

 

Wouldnt my stock heads be NPI then? So if i port them and do a PI cam and intake swap, i should make some good power..

 

Yup, your stock heads should be NPI, although check what your ports look like as it was 1999 when they changed from NPI to PI. I suggested picking up another set of heads so you wouldn't have downtime with your truck and they are fairly cheap.

http://www.babcox.com/editorial/ar/eb40228.htm
Check out this site as 1999 was the year that Ford switched to PI and also there were Romeo and Winsor 4.6s.

 

You could have either PI or NPI in '99 with a 4.6L, it is a mess of when exactly Ford switched the 4.6L's over on the F150's. check the heads first, you may already have them, than as said above most of the power comes from the intake, if you just swap the intake you have to plug some coolant passages with RTV.

Here is a site detailing the intake swap in a car, everything will more or less be the same. I don't think there is any difference in the top end where it is important for this swap when talking romeo Vs. Windsor:

http://www.redpulsar.us/~coldfusion/intakeswap.html

That babcox site is GREAT for modulars pre '00

 

Romeo Vs. Windsor heads have different valve covers. That's about it.

 

Romeo motors had bolt-on cam gears whereas the Windsors were press on.
Romeo motors used 6 bolt cranks where as the Windsors had 8 and some 6 bolt cranks.
Romeo motors used press-fit rods, Windsors were full floating
Pistons were a little different.
There are small differences in the heads which the site I posted explains.
There were a number of different front timing covers depending on the model and year

Just make sure that you know what motor you have and what motor your parts are coming off of.

 

Great information.

The cam swap isn't hard at all. We didn't even take the timing cover off when we did it on a friend's Mustang. I forgot to mention the RTV, thanks. The NPI gaskets work best with the RTV. Here are some of the pictures from when we did the intake/cam swap. I wish I had taken more...

http://mistercmk.com/album/thumbnails.php?album=12

 

Ya I had already check to see if i had the PI heads and as far as i could see or "couldnt see" there was no PI above the manifold... so im the unlucky one.. but my truck runs like a striped ape now.... so with this mod it should even run better.

 

Yup, its amazing what the cams will do for the vehicle. Your exhaust note will probably be a little tamer, but it will pull harder.