I have a 2004 Ford Heritage with the 4.6. What are the stock cam specs? My other question concerns the cylinder heads. Are the cylinder heads PI or non-PI. Thanks for your help.

 

They are PI.

 

Stock PI cams are .510" intake and .530" exhaust lift.
JL

 

Can some one educate me on the difference between the PI and non PI heads and while they are at it what PI means?
Thanks
Zach

 

Ford changed the intake ports ,exhaust ports, and comustion chamber on their 2V heads in '99. The 5.4L and the Mustang 4.6L got them in '99. They flow a slight bit more on the exhasut side,and are approximately the same on the intake side than the non-PI parts. The cams also changed to have more lift (on all applications with PI heads) and they have a better flowing intake manifold to make the power jump from 225hp to 260hp in the Mustang's case.
PI is know as "power improved" or performance improved". In all honesty-the head castings themselves are almost equivalent for flow and performance when equally equipped for cams and intakes. The short side radius and the shape of the intake ports on the PI are terrible for flow,and the runner size is a bit large with very little taper,and this hurts high lift flow and velocity. The NPI port is much better for a N/A application due to this-when SC'd they're the same since you're introducing cylinder fill via positive pressure. PI's are slightly better on the exhaust side due to the port change and are slightly better than the NPI when used in a SC'd application.
Basically-either head is good-you just need to make a choice on which one you want,and work with it from there. IMO-I'd use a PI head for a SC applcation,and a NPI for a N/A application.
JL

 

Thanks for that clarification I have been seein that term in these threads for along time and now I know.
Basically when they started using PI heads they improved the exhaust flow and changed the cam to get more power?
And a naturally aspirated engine runs better with the non PI heads. And a turbo or supercharged engine would be more suited to the PI heads.
In lamens terms just to make sure I got the jist of what you were saying.

 

That's pretty much it-with all else equal-the heads themselves are very close to being equivalent with each having a slight advantage in one way.
N/A-NPI
SC-PI
If you want to do some reading on this to back up my claims,read the following thread and the threads linked in it:
http://forums.modulardepot.com/4-6l-...-npi-data.html
JL

 

I appreciate the feedback. If you replaced the stock PI heads with ported and polished heads and a more aggresive cam, what kind of HP and torque increases can you expect to see? I'm debating on whether to bolt on a supercharger or stay N/A. Thanks in advance.

 

If you leave the truck intake-you'll only have minimal gains with a set of cams and ported heads.Truck intakes are terrible for flow-the're made for low RPM cylinder fill,and this sacrifices the ability to flow enough air at high RPM to feed a modified engine.They're actually very restrictive to the bone-stock engine. Now,a SC would alleviate this problem since the air is fed to the engine under pressure,but unless it replaces the intake-you're still going to have issues with airflow at some point.
JL

 

What is a good solution for the restrictive intake?

 

For a truck,there isn't one,unless you use a car intake on it,and that'll hurt your low end in a heavy truck.Now,if it's SC'd,most of the positive displacement SC's replace the manidfold. If you get a cetrifugal SC,then a car intake can be used-you'll keep some of the low-end torque due to the SC and the positive pressure you'll have on the intake.
JL

 

I've been looking at both the positive displacement and centrifugal supercharger systems. What is your suggestion?

 

For a truck-PD,no question.
JL

 

Thanks for all of your help. It's greatly appreciated.

 

Kenne-Bell makes nice superchargers for these engines.