I have a 97 4.6 and in my manual it says the engine cranks out 210 hp and 290 lb-ft of torque. In a friend of mine's 01 4.6 his says 231hp and 293 lb-ft of torque. What did they improve?

 

PI heads, introduced on late 98 models, I believe. All 99's and up have them.

 

What do you mean by PI heads? What is it?

 

PI=Power Improved different and better head design.

 

Some where on one of the message boards I saw someone said it was different intake manifolds. Have any of you heard of that?

 

You need a the PI-style intake manifold because the non-PI manifold won't bolt up to the PI heads.

But that's just for fitment, the heads are responsible for the power gains.

Here's some info from guys (Raider & Neal) who post here and on Crash's site:
http://www.got-pressure.com/yabbse/i...;threadid=2909

 

Thanks Jordan not Mike for the post. I think I'll just leave my heads alone considering how tight every thing is in there and just enjoy what I've got.

 

I've been reading on the Mustang Forums about the PI Heads. There are a few there that claim they get similar HP gains by just using PI cams, and PI intake on Non-PI Heads. I have also read that non PI heads actually outflow PI heads at higher lift.
I know we aren't talking about Mustangs here, but couldn't we expect similar results on our trucks?

 

yeh. u get same gains by going to pi heads as u would with a mustang.. but its alotta work.. but its inexpensive to do

 

I think you misunderstood me.....
My point was they are getting similar horsepower out of just PI cams and PI intake on Non PI heads. Kind of taking the PI heads out of the equation. I think it was Ted98 that showed the difference in intakes was minimal on our trucks, so maybe this swap wouldn't show much in gains.
Was just curious if anyone had done it this way, and had any success.