different bhp for 4.6's -why?

the 96-98 4.6L had a set of heads that while they were pretty decent, they just couldn't perform at all in the upper rpm's. ford then revised this in 99 with PI or performance improved heads. these heads flowed significantly better than the previous years heads. this was also accompanied by a better performing intake as well. this is the reason why 2v 4.6L in 99-04 make 260hp. also the 96-98 4.6L used coil packs and spark plug wires. while the 99+ use COP or coil-on plug design.

if you want to make 300hp get the PI heads with a good port job. some cams, an upper plenum or an new intake all together. although that could be pricey depending on which intake you would choose. maybe some pullies and a timing advancer. the heads, cams, and intake combo will be where you'll make the most power in conjunction with the exhaust.

The best way to go would be to get a Mach 1 4.6L. Those have 305hp. Or you could get a '01 Cobra 4.6L which has 320hp. Both are DOHC V8's.

They are also rated at the flywheel so it is technically FWHP, not bhp.

If you want 300fwhp, you will need most of the stand bolt ons.

Bornstanger said:

the 96-98 4.6L had a set of heads that while they were pretty decent, they just couldn't perform at all in the upper rpm's. ford then revised this in 99 with PI or performance improved heads. these heads flowed significantly better than the previous years heads. this was also accompanied by a better performing intake as well. this is the reason why 2v 4.6L in 99-04 make 260hp. also the 96-98 4.6L used coil packs and spark plug wires. while the 99+ use COP or coil-on plug design.

if you want to make 300hp get the PI heads with a good port job. some cams, an upper plenum or an new intake all together. although that could be pricey depending on which intake you would choose. maybe some pullies and a timing advancer. the heads, cams, and intake combo will be where you'll make the most power in conjunction with the exhaust.

Click to expand...

Any proof that the PI Heads flow significantly better than the NPI's?

The big difference between 96 - 98 NPI headed cars and 99 - 04 PI headed cars is the more aggressive cam in the PI head and the better intake in the 99+ cars. The stock NPI head flows almost the exact same as the stock PI head on the intake side, but is outflowed on the exhaust side.

Another thing I would like to add is that I have been a member of TCCOA for quite a few years. The reason I bring this up is I remember when the "IN" thing to do was the PI Head Swap and PI Motor Swap. The "PI" motor powered TBirds through 4R70W and IRS are making between 210 and 230 HP at the wheels. NPI powered Tbirds with the 4R70W and IRS with PI cams and PI intake are making between 210 and 230 HP at the wheels. Same compression ratio, same intake, same cams = same power!

PI Head Swap on a NPI car will yeild a higher compression which will give you another 10 - 15 HP, but that has nothing to do with the head flow.

yeah, I'd definitely go w/the 4.6 DOHC mod motor and just be done w/it

TGJ said:

Any proof that the PI Heads flow significantly better than the NPI's?

The big difference between 96 - 98 NPI headed cars and 99 - 04 PI headed cars is the more aggressive cam in the PI head and the better intake in the 99+ cars. The stock NPI head flows almost the exact same as the stock PI head on the intake side, but is outflowed on the exhaust side.

Another thing I would like to add is that I have been a member of TCCOA for quite a few years. The reason I bring this up is I remember when the "IN" thing to do was the PI Head Swap and PI Motor Swap. The "PI" motor powered TBirds through 4R70W and IRS are making between 210 and 230 HP at the wheels. NPI powered Tbirds with the 4R70W and IRS with PI cams and PI intake are making between 210 and 230 HP at the wheels. Same compression ratio, same intake, same cams = same power!

PI Head Swap on a NPI car will yeild a higher compression which will give you another 10 - 15 HP, but that has nothing to do with the head flow.

Click to expand...

NPI PI NPI PI

1. .050 25 25 22 24
2. .100 47 51 40 49
3. .150 64 76 60 68
4. .200 83 102 80 84
5. .250 99 124 96 96
6. .300 114 138 108 107
7. .350 125 149 112 116
8. .400 136 153 115 123
9. .450 147 155 116 130
10. .500 156 156 117 133
11. .550 163 169 117 136

No difference huh?

artificial HP said:

NPI PI NPI PI

1. .050 25 25 22 24
2. .100 47 51 40 49
3. .150 64 76 60 68
4. .200 83 102 80 84
5. .250 99 124 96 96
6. .300 114 138 108 107
7. .350 125 149 112 116
8. .400 136 153 115 123
9. .450 147 155 116 130
10. .500 156 156 117 133
11. .550 163 169 117 136

No difference huh?

Click to expand...

Where did you get those? I don't have the exhaust numbers handy right now, but I grabbed these from an old post of mine at MD.

Same day, same testing procedure

Intake side:

NPI1
.100...46
.200...84
.300...121
.400...147
.500...170

NPI2
.100...52
.200...91
.300...119
.400...144
.500...168
.600...177

PI1
.100...50
.200...93
.300...126
.400...148
.500...158
.600...163


Your point being? If you are going to quote SHM, better get their stats right! Even SHM has the NPI outflowing the PI at higher lift.

Where you got your stats from:

http://www.modularfords.com/forums/attachment.php?attachmentid=9107&stc=1

Nevermind, those are Sean Hyland's numbers.

TGJ said:

Where did you get those? I don't have the exhaust numbers handy right now, but I grabbed these from an old post of mine at MD.

Same day, same testing procedure

Intake side:

NPI1
.100...46
.200...84
.300...121
.400...147
.500...170

NPI2
.100...52
.200...91
.300...119
.400...144
.500...168
.600...177

PI1
.100...50
.200...93
.300...126
.400...148
.500...158
.600...163


Your point being?

Click to expand...

Look dude im not trying to be a dick or nothing but the valves are so different in size that you can see it. Look around for pictures because I have seen one on here before that showed the size difference and that was obvious to the human eye. Those #s are off. PI heads really brought the sohc mod motors to life. Cam profile and lift is also different but PI heads flow a good bit more of air then NPIs.

modmonster said:

Look dude im not trying to be a dick or nothing but the valves are so different in size that you can see it. Look around for pictures because I have seen one on here before that showed the size difference and that was obvious to the human eye. Those #s are off. PI heads really brought the sohc mod motors to life. Cam profile and lift is also different but PI heads flow a good bit more of air then NPIs.

Click to expand...

I am not trying to be a dick either but the PI heads are not better than NPI. It was not the PI heads that brought the 4.6L SOHC to life. Kris Danner and Johnny Langton proved that.

Way back in 99, 00, 01, 02, people were looking to modify 4.6L Tbirds. The easiest thing was the PI HeadSwap. For the 94 - 95 TBird guys, it was hardly cost anymore to swap in a PI motor as those TBirds required a bunch of 96+ plus parts to do the headswap. Like I stated above, these "PI" powered birds are/were making 210 - 230 HP at the wheels. Big Scott or Dr.FrankenCougie depending on what forum you are on does a N/A PI buildup. He used Fox Lake P&Ped PI heads/PI cams/Intake/Forged internals in his 94 Cougar and put down 256 RWHP.

Along comes Johnny Langton, he is the first to swap "PI" Cams into NPI heads, gained 13 RWHP from it. He then gets his NPI Heads port and polished and is aiming to run 12's. He then finds out that his car runs out of air at around 4000 RPM. He thinks the NPI intake is the restriction, so him and Kris Danner modify a PI intake to fit his car. He then gains 17 RWHP and 39 RWHP at the peak. Johnny's 97 Tbird made 254 RWHP with this setup. 2 less HP than Scott did with similar all around mods. They had the same cams, intake, compression ratio and all around mods, ie. exhaust.

He took a lot of crap from people when he did the cams, he took a lot of crap from people when he did the intake. People were questioning the what Johnny had done.

Kris then went on to show by putting PI Cams and PI intake on a stock 96 Cougar, he made 217 RWHP, which is right on par with what PI Powered Tbird/Cougars were making. A few other people have gone out and did this as well and the numbers are ranging from 212 - 228 HP at the wheels. Identical to PI motor/head cars. All being equal, compression, cams, intake, the PI's are not making any more power than the NPI's and if they really flowed more on the intake side in an N/A application, they should be making more power but they are not making any more.

Anyway, I happen to know the valve sizes of both PI and NPI heads. I don't need to see pictures.

PI head valves:

Intake...1.75"
Exhaust...1.41"

NPI head valves:

Intake...1.75"
Exhaust...1.33"

The valve sizes came from a very trust worthy source. Head flow numbers are all dependant on how they are done. Everybody( Fox Lake, SHM, etc. ) has different flow #'s. The numbers I got also came from a very trust worthy source. Those NPI's #'s I posted are from the F5( 96 -98 ) casting, what did SHM use? Did they use the garbage F4( 91 - 95 ) casting?

I am not going to debate PI VS NPI any further, I am done with this. You can want to believe the PI head is better but it has been proven that the head itself is no better than the NPI.

wow at all this bull****. PI heads blows NPI heads out of the water. Look at the intake ports and combustion chambers, that is all you need to see.


no NPI head car has ever made the power PI heads do. again, NPI heads suck.

i guess i should ask this question then. why did ford spend all that time and money on developing new design castings for the heads, when all they had to do was just design a new intake and cams? now i admit not all things a car company does make sense. but this one seems to, unless ford likes throwing money away.

mogs01gt said:

wow at all this bull****. PI heads blows NPI heads out of the water. Look at the intake ports and combustion chambers, that is all you need to see.


no NPI head car has ever made the power PI heads do. again, NPI heads suck.

Click to expand...

Nick, I am kind of surprised with your moronic response. What about the NPI N/A cars faster than you, Nick? I mean Johnny Langton took a NPI N/A Tbird to the 12's with P&Ped NPI heads, Comp Cams, Plastic PI Intake, 3500 stall TC and 3.73's with IRS. What did you run with your P&Ped PI's with comp cams, 3.90's 5spd and solid axle, not to mention a 600 lb weight advantage? Oh yeah, 13.2! Those NPI's sure suck don't they? I am not going to argue with morons/idiots anymore on this.

As for that question about why Ford did that, I don't know the answer to that.

12 huh? WOW. PI heads are in the 10s man.

13.2 yep, that is it. On a engine that was missing and over heating. Not to mention that my rear end is blown.

if you want to be slow, listen to TGJ.

i think the name PI says it all Perfomance improved........(if thats the actual meaning or not i dont know)

mogs01gt said:

12 huh? WOW. PI heads are in the 10s man.

13.2 yep, that is it. On a engine that was missing and over heating. Not to mention that my rear end is blown.

if you want to be slow, listen to TGJ.

Click to expand...

PI = Performance Improved.

Oh, Now the excuses are out. Did the car break at the track? If not, why did you run it knowing that it was broken?

Listen to me, if you want to go slower? I degreed my camshafts when I put them in and I tell everyone to degree their camshafts when installing them. Can you say that you do the same? I never said the PI heads are garbage nor did I imply it. What I said is that the head itself makes no more power than the NPI and it doesn't.

I know KenB is in the 10's with a gutted race car. His current motor would not run 10's in a full weight mustang and no where near it. Comparing Ken's car to Johnny's is absurd, there is over a 1000 lbs difference, JL has IRS and an auto, KB has solid axle and 5 spd, KB has a far better intake, better cams, higher compression as well. I compared your car to JL's as they had more in common than JL's and KB. Your car has the advantages and the Superior heads as you guys are putting it and is running slower.

People gave up on the NPI's a long time ago and it was not until Johnny Langton started something with the NPI's did the NPI's get noticed. Give it time and you will see even more examples of the NPI's putting the HP and 1/4 numbers that the PI heads are.

Like I said, the proof is out there about what I said. A NPI headed car with the same cams, same intake, same compression, same mods, transmisson and rear gears will make the same power as the PI headed car, stock or P&Ped. The only exception to that right now is Cobra Kller's P&Ped PI head, but that head is only good for forced induction. I am not against PI heads, if I was to run a full blown SCed 2V car, there is no doubt which heads I would use, they are Cobra Killer's PI heads without question. I am tired of everyone knocking the NPI head when it is not the head that was the restriction in the 96 - 98 4.6L 2V Motor.