HP gain from P&P npi heads?

98COBRA281 · Jun 4, 2008

well my friend and i just got a 97 4.6 motor out of a lincoln for free, i rely want to port and polish the heads for my car, i have done a lot of porting, and port matching on 2 strokes before so im pretty good at it, and have all the tools, i know you can port npi to flow almost as good as pi heads, and for compression, i have had heads shaved a few thousanths before to raise compression on push rod motors, but never on a mod motor, can this be done on a mod motor, or does it cause a problem with the timing chains,and tensioners?, and would it be worth it?

flstang65 · Jun 4, 2008

id just get some pi heads and p&p them

CobraRed_96_GT · Jun 4, 2008

Up top NPI ported heads flow BETTER, just not as much low rpm/lift flowage as a pi ported head. plus you keep low compression

flstang65 · Jun 4, 2008

CobraRed_96_GT said:
Up top NPI ported heads flow BETTER, just not as much low rpm/lift flowage as a pi ported head. plus you keep low compression

cool, thanks for the info

TGJ · Jun 4, 2008

CobraRed_96_GT said:
Up top NPI ported heads flow BETTER, just not as much low rpm/lift flowage as a pi ported head.

This info is incorrect...

My Renegade Racing P&P NPI heads out flow Fox Lake Stg 2 P&P PI heads from .050 lift to .650 lift on both the intake and exhaust sides.

98COBRA281 · Jun 4, 2008

so would it be worth all the work? what hp gain should i expect? and how about shaving them, has anyone done it to raise compression

TGJ · Jun 4, 2008

Personally, I would not shave the heads to gain compression, I would change out the pistons. If rebuilding the engine is not what you want to do and you want a higher compression ratio, get the PI heads. A friend of mine quite a few years ago saw a 25 - 30 RWHP gain in his 97 NPI TBird by going to Renegade Racing P&P NPI heads over stock NPI heads. He ran stock PI cams and the stock NPI intake. In fact he was the first person to put PI cams and a PI intake on a NPI engine without the PI heads...

98COBRA281 · Jun 4, 2008

TGJ said:
Personally, I would not shave the heads to gain compression, I would change out the pistons. If rebuilding the engine is not what you want to do and you want a higher compression ratio, get the PI heads. A friend of mine quite a few years ago saw a 25 - 30 RWHP gain in his 97 NPI TBird by going to Renegade Racing P&P NPI heads over stock NPI heads. He ran stock PI cams and the stock NPI intake. In fact he was the first person to put PI cams and a PI intake on a NPI engine without the PI heads...

so i guess ill just do a Bad A$$ port job on them, i would love to buy P&P pi heads, but some of you know im only 16 years old, and have a wine taste with a beer pocket , and want more power bad

Winters98GT · Jun 5, 2008

TGJ said:
Personally, I would not shave the heads to gain compression, I would change out the pistons. If rebuilding the engine is not what you want to do and you want a higher compression ratio, get the PI heads. A friend of mine quite a few years ago saw a 25 - 30 RWHP gain in his 97 NPI TBird by going to Renegade Racing P&P NPI heads over stock NPI heads. He ran stock PI cams and the stock NPI intake. In fact he was the first person to put PI cams and a PI intake on a NPI engine without the PI heads...

would that be Johnny?

I personally would not port NPI heads, and most def. if your not doing the labor on swapping the heads. just not worth it NPI. A couple cars have gone very fast NA with ported NPI's, but I just wouldnt trust most porters with NPI/NA heads, not too many people have experience with them. The ones that do, still charge quite a bit and its not woth it if you have to drop another 1000-1200 on the install and a new tune for 20rwhp.

CobraRed_96_GT · Jun 5, 2008

TGJ said:
This info is incorrect...

My Renegade Racing P&P NPI heads out flow Fox Lake Stg 2 P&P PI heads from .050 lift to .650 lift on both the intake and exhaust sides.

Huh? That's what i said, PI ported heads outflow in low rpm and early in the lift cycle (which is why i said low rpm/lift). Hence your heads flow better from .50-.65 which is high lift...

TGJ · Jun 5, 2008

Winters98GT said:
would that be Johnny?

I personally would not port NPI heads, and most def. if your not doing the labor on swapping the heads. just not worth it NPI. A couple cars have gone very fast NA with ported NPI's, but I just wouldnt trust most porters with NPI/NA heads, not too many people have experience with them. The ones that do, still charge quite a bit and its not woth it if you have to drop another 1000-1200 on the install and a new tune for 20rwhp.

Yes, it would be JL...

Renegade Racing NPI heads are priced very competively with most ported PI heads. All of us quick N/A NPI guys all have his NPI Heads.

CobraRed_96_GT said:
Huh? That's what i said, PI ported heads outflow in low rpm and early in the lift cycle (which is why i said low rpm/lift). Hence your heads flow better from .50-.65 which is high lift...

Go read what I posted again...

I will make it clear...

My NPI heads outflow Fox Lake's PI Stg 2 P&P Heads across the board, right from low level lift( .050 ) to high lift( .650 )... Which is what I posted earlier, it was not a mistake... Hence your post is incorrect.

Edit:

My original post, note at the bottom, it DOES NOT say lasted edited by...

TGJ said:
This info is incorrect...

My Renegade Racing P&P NPI heads out flow Fox Lake Stg 2 P&P PI heads from .050 lift to .650 lift on both the intake and exhaust sides.

BennyBlown2v · Jun 5, 2008

CobraRed_96_GT said:
Huh? That's what i said, PI ported heads outflow in low rpm and early in the lift cycle (which is why i said low rpm/lift). Hence your heads flow better from .50-.65 which is high lift...

reading comprehension > CobraRed apparently! Jk brotha

Go for porting the NPI head! With the money you save, go get a CNC valve job done while you're at it, can't hurt!

Green&GoldGT · Jun 5, 2008

Ok, yes when NPI heads are ported to the max they flow better up top, referring to the amount of lift in the cam. But that is only around .600" lift and chances are your cam doesn't reach that high or spend most of its time there. Camshafts in 4.6 mustangs spend most of their time in mid lift, so you want as much flow in around .400-.450" of lift or so. The reason why PI heads are better is because they flow better in the mid lift of the cam.

When looking for heads don't compare how much they flow at .600" of lift. And even if your heads flow more cfm, it doesn't mean that you're going to make more hp. You can't hog out 4.6 heads to make power. It's more important that each port flows the same.

Don't shave your heads on a 4.6 to make compression, it will have sealing issues. Just buy a set of PI heads to raise compression and flow.

CobraRed_96_GT · Jun 5, 2008

ok so i read .50 instead of .05 - calm down. I've seen previously posted numbers:
Lift in Inches – Non-PI (’96-‘98) – PI (’99-’04)

.100 – 061 – 060
.150 – 089 - 086
.200 – 112 - 116
.250 – 131 - 141
.300 – 146 - 160
.350 – 160 - 169
.400 – 173 - 176
.450 – 185 - 182
.500 – 188 - 185
.550 – 193 - 186

And talking personally with the guy who ports mustangs heads at Total Performance where he tested to two on a flow bench, and the guy who bought the ported NPI heads after having a pair of ported PI heads for 2 years that they (according to his dyno results) flow better primarily up top. HENCE either this is true or porting NPI heads isn't uniform across the board - so don't go around saying people are incorrect when you have the narrow perspective of one instance.

TGJ · Jun 5, 2008

CobraRed_96_GT said:
ok so i read .50 instead of .05 - calm down. I've seen previously posted numbers:
Lift in Inches – Non-PI (’96-‘98) – PI (’99-’04)

.100 – 061 – 060
.150 – 089 - 086
.200 – 112 - 116
.250 – 131 - 141
.300 – 146 - 160
.350 – 160 - 169
.400 – 173 - 176
.450 – 185 - 182
.500 – 188 - 185
.550 – 193 - 186

And talking personally with the guy who ports mustangs heads at Total Performance where he tested to two on a flow bench, and the guy who bought the ported NPI heads after having a pair of ported PI heads for 2 years that they (according to his dyno results) flow better primarily up top. HENCE either this is true or porting NPI heads isn't uniform across the board - so don't go around saying people are incorrect when you have the narrow perspective of one instance.

NPI head porting by companies is different. EVERY SET of Renegade Racing's NPI heads outflow across the board to comparable P&P PI heads. Renegade Racing is a hobby for the guy that does the work. He works for Ford as a engineer in advanced powertrain during the week. His knowledge on the Modular V8/V10 is quite extensive. It's the very reason his NPI's are the best P&P NPI's out there.

His P&P PI's don't have the best flow numbers but perform better than most of the P&P PI heads out there from what I have seen as well. Had I used PI heads, they would have been his. When I talked to him about my build, he suggested to me that if I stay N/A and under 11:1 compression ratio, to use NPI heads. If I was going above 11:1 compression, the SVO heads I had might be better. If I was going to add FI in the future to use PI heads.

Since I was staying N/A, I went with his NPI heads. Do his heads work? Last time I checked, I am still the most powerful N/A streetable 2V on this board with an automatic. JL has had great success with his NPI heads, Hans as well...

98COBRA281 · Jun 5, 2008

TGJ said:
Do his heads work? Last time I checked, I am still the most powerful N/A streetable 2V on this board with an automatic. JL has had great success with his NPI heads, Hans as well...

more details about you car please

CobraRed_96_GT · Jun 5, 2008

TGJ said:
NPI head porting by companies is different. EVERY SET of Renegade Racing's NPI heads outflow across the board to comparable P&P PI heads. Renegade Racing is a hobby for the guy that does the work. He works for Ford as a engineer in advanced powertrain during the week. His knowledge on the Modular V8/V10 is quite extensive. It's the very reason his NPI's are the best P&P NPI's out there.

His P&P PI's don't have the best flow numbers but perform better than most of the P&P PI heads out there from what I have seen as well. Had I used PI heads, they would have been his. When I talked to him about my build, he suggested to me that if I stay N/A and under 11:1 compression ratio, to use NPI heads. If I was going above 11:1 compression, the SVO heads I had might be better. If I was going to add FI in the future to use PI heads.

Since I was staying N/A, I went with his NPI heads. Do his heads work? Last time I checked, I am still the most powerful N/A streetable 2V on this board with an automatic. JL has had great success with his NPI heads, Hans as well...

Good info to know. Does he have any flow charts?

Like this:

http://www.mediafire.com/?nk0zk4lgl3x

And i do recognize every porter is different and instrumentation used to test flow changes, just think it'd be a good idea for a tech thread.

Looks like in this case the NPI head has a small advantage early in the lift cycle as well

96GT281 · Jun 5, 2008

the p&p npi heads from the lincoln are going on my car but 98COBRA281 doesnt know tht im buying longtubes and an o/r h pipe that he wants so bad. they are on ebay for $180 so ill just throw those in when we do the heads.

98COBRA281 · Jun 5, 2008

96GT281 said:
the p&p npi heads from the lincoln are going on my car but 98COBRA281 doesnt know tht im buying longtubes and an o/r h pipe that he wants so bad. they are on ebay for $180 so ill just throw those in when we do the heads.

and im getting the heads off your car..... with 20k less miles , long tubes on your stock npi.......maybe 7 horse power

96GT281 · Jun 6, 2008

98COBRA281 said:
and im getting the heads off your car..... with 20k less miles , long tubes on your stock npi.......maybe 7 horse power

yea but for $180 i might as well buy them now instead of paying 500 down the road

HP gain from P&P npi heads?

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