thanks man...
whats the OEM lift?
whats the OEM lift?
Anybody hand-port their NPI heads?
- Thread starter Burninrock24
- Start date
Wichers123
Well-Known Member
It's like 480ish for npi and 530ish for the pi's both have the same duration and lsa
OP
OP
Burninrock24
Active Member
I mean yeah, it's an old book. SN95s are 9-17 years old too. There isn't much more up to date that you can get over stock flow numbers.
The npi heads are still contenders in the 2v battles, ....they just need a little more love.
1. The intake valve has that darn swirl dam to help promote swirl. Laying the dam back a little will unshroud the valve and help with flow, but dont cut it out totally. We still want lots of swirl. Removing it totally will increase advance timing. Also removing the material of the combustion chamber around the valve, laying back to the gasket/ bore size helps a lot. This reduces the chamber cc but makes a word of difference in flow. From my discoveries with pi vs npi 4.6l rwhp differences with stock untouched heads the pi was only 10rwhp more different over the npi all in stock form with same HEAD CAM INTAKE (PI) and compression. Doing this swirl dam trick places the rwhp equal between the 2 but the npi torque is alittle more.....both tested at the same compression!
2. The npi exhaust valve is smaller of the heads but not really a wall for flow. I believe Ford switched the exhaust valve size to a 4v intake valve size to cut down on manufacturing.(a 4v intake valve is much long than a 2v valve and will not directly swap) This flow wall is the material around the valve guide under the npi exhaust valve. You can really go crazy removing this material but leaving a little at the roof of the port to aid in some support for the guide. Doing this takes a port that stalled air flow at just .300" lift to an accelerated flow to max lifts.
3. The intake port actually is pinched early into the port. More pinched than the tear drop shape you see at the manifold side. The manifolds ports are actually bigger! Again opening this up improves flow.
4. The valve guide length is what kills the use of a higher lift cam. Simply grind off around .150" off the top of the guide under the valve springs. This will add clearance between keepers/retainer and valve seal. Only do this if you plan to use a higher lift cam with more than .550" lift. If you do this modification a different valve seal must be used. Instead of a 2v seal get 4v valve seals. The 4v seals are shorter than 2v. The typical remedy is to deepen the spring pocket and cut the top off the guide to fit the 2v seal.
5. Their is to much combustion chamber. You're better to mill the heads .100" and compensate the compression with piston dish. Keeping all the combustion in the cylinder head as much as possible and not in the cylinder is more beneficial to flame travel/combustion characteristics/timing. The combustion chamber is essentially the same as a pi, just more of it. Also the deck thickness on most npi heads are roughly .080" more than any pi head. Earlier npi heads are .150" thicker.
6. Port the ports! You can literally take .100" from the walls off the intake port walls. All the way around! So a port I.d. of 1.400" to 1.600" is possible. That's crazy! Same material for the exhaust but their is more material on the floor than the roof.
Intake valve: Rough untouched under the valve seats. Blend the bowl with little material removed keeping it rough. Cut out the rest of the port from there. Port the floor short radius under the seat keeping a good radius but opening it up from there. Open the sides up also. All this while trying to keep a funneling shape in mind.
1. The intake valve has that darn swirl dam to help promote swirl. Laying the dam back a little will unshroud the valve and help with flow, but dont cut it out totally. We still want lots of swirl. Removing it totally will increase advance timing. Also removing the material of the combustion chamber around the valve, laying back to the gasket/ bore size helps a lot. This reduces the chamber cc but makes a word of difference in flow. From my discoveries with pi vs npi 4.6l rwhp differences with stock untouched heads the pi was only 10rwhp more different over the npi all in stock form with same HEAD CAM INTAKE (PI) and compression. Doing this swirl dam trick places the rwhp equal between the 2 but the npi torque is alittle more.....both tested at the same compression!
2. The npi exhaust valve is smaller of the heads but not really a wall for flow. I believe Ford switched the exhaust valve size to a 4v intake valve size to cut down on manufacturing.(a 4v intake valve is much long than a 2v valve and will not directly swap) This flow wall is the material around the valve guide under the npi exhaust valve. You can really go crazy removing this material but leaving a little at the roof of the port to aid in some support for the guide. Doing this takes a port that stalled air flow at just .300" lift to an accelerated flow to max lifts.
3. The intake port actually is pinched early into the port. More pinched than the tear drop shape you see at the manifold side. The manifolds ports are actually bigger! Again opening this up improves flow.
4. The valve guide length is what kills the use of a higher lift cam. Simply grind off around .150" off the top of the guide under the valve springs. This will add clearance between keepers/retainer and valve seal. Only do this if you plan to use a higher lift cam with more than .550" lift. If you do this modification a different valve seal must be used. Instead of a 2v seal get 4v valve seals. The 4v seals are shorter than 2v. The typical remedy is to deepen the spring pocket and cut the top off the guide to fit the 2v seal.
5. Their is to much combustion chamber. You're better to mill the heads .100" and compensate the compression with piston dish. Keeping all the combustion in the cylinder head as much as possible and not in the cylinder is more beneficial to flame travel/combustion characteristics/timing. The combustion chamber is essentially the same as a pi, just more of it. Also the deck thickness on most npi heads are roughly .080" more than any pi head. Earlier npi heads are .150" thicker.
6. Port the ports! You can literally take .100" from the walls off the intake port walls. All the way around! So a port I.d. of 1.400" to 1.600" is possible. That's crazy! Same material for the exhaust but their is more material on the floor than the roof.
Intake valve: Rough untouched under the valve seats. Blend the bowl with little material removed keeping it rough. Cut out the rest of the port from there. Port the floor short radius under the seat keeping a good radius but opening it up from there. Open the sides up also. All this while trying to keep a funneling shape in mind.
OP
OP
Burninrock24
Active Member
You. I like you.
I have an issue with no 5 though. Since it's a timing chain, I've heard there isn't much room to play with in order to keep proper chain tension. Any feedback on this?
I have an issue with no 5 though. Since it's a timing chain, I've heard there isn't much room to play with in order to keep proper chain tension. Any feedback on this?
Wichers123
Well-Known Member
It's hydraulic tensioners its should take the little slack your gonna add.
This is true, but their is plenty of room to compensate. Yes their may be to much slack after a .050" shave, but just get new chain guides. A .050" head deck really is not a lot of material to cause a problem that can't be compensated. With this done , the cams will need degreeing....no factory setting will work.
Notice the port entrance is pinched. Early in the port, the floor is raised and ascends very little leading into the short radious. The short radoious and roof/bowl and sides in that area are the most open portion of the port.
At port entrance the roof opens up more than the actual port/gasket , but then is pinched about a inch itnto it. From the pinched area the roof flows into a raise
This port is nothing like a pi heads swirl/high tumble shape. Npi is strictly swirl! There is no funnel affect with this port like every intake port known. The funnel causes the incoming air to speed up before being displaced by the valve. We wanna keep the swirl damn to promote swirl but not all of it. Laying it back some helps unshroud the valve, but don't completely eliminate it. This will kill the swirl affect and give the incoming mixture an undirected path, even though the port will flow really good. This is proof that a flow bench results can be a hoax. Homogeneous mixture is the goal!
Notice how the valve angle correlates with the port and how the mass incoming air flows over the valve. This is key for the high swirl motion in the cylinder and we want to retain that. The more the swirl affect, the better the motion, the better atomized mixture, and with all this....the more timing we can run! The better the burn .....just better all around. This is where the pi heads and ports are superior to the npi and to boot, the pi heads have a quiched area for that incoming rushed mixture to be squished into a tighter area before ingnition happens essentially creating less area for flame travel. Beautiful! !
The flow bench only test flow amount from a hole! The flow bench can not show what happens after the incoming rush mixture enters that hole. This is the hoax of the flow bench. Sure the port flows to ablievion but as the piston moves to BDC that atomized mixture has no path and is recreating itself as a liquid on your cylinders walls, piston top, and reduced timing.
Notice how the valve angle correlates with the port and how the mass incoming air flows over the valve. This is key for the high swirl motion in the cylinder and we want to retain that. The more the swirl affect, the better the motion, the better atomized mixture, and with all this....the more timing we can run! The better the burn .....just better all around. This is where the pi heads and ports are superior to the npi and to boot, the pi heads have a quiched area for that incoming rushed mixture to be squished into a tighter area before ingnition happens essentially creating less area for flame travel. Beautiful! !
The flow bench only test flow amount from a hole! The flow bench can not show what happens after the incoming rush mixture enters that hole. This is the hoax of the flow bench. Sure the port flows to ablievion but as the piston moves to BDC that atomized mixture has no path and is recreating itself as a liquid on your cylinders walls, piston top, and reduced timing.
Ahhh its like 1999 again in here 
I remember going through all of this.
The NPIs can be ported and have = flow as a ported PI. The big issue was the lack of a decent intake manifold that was obtainable at a reasonable price.
We all wanted the SVO Intake but the intake and install kits were expensive and hard to find so thats when people starting experimenting with swapping PI parts.
First was the cams, then the Intake, then just a full PI swap that upped compression for cheap power.
There was a guy out in like Minnesota who was porting NPI's for the 4.6 Tbird/Cougar guys that flowed as much as the best ported PI's. Jim was the first name, can't remember the last but he did nice work and his heads were in demand. His ported SVOs were even better. The lack of the intake just didn't let the work shine though.
Ford pulled the plug way to fast with the 2V support. In the beginning we had heads/intake and even the blower but they didn't make enough of them.
I remember going through all of this.
The NPIs can be ported and have = flow as a ported PI. The big issue was the lack of a decent intake manifold that was obtainable at a reasonable price.
We all wanted the SVO Intake but the intake and install kits were expensive and hard to find so thats when people starting experimenting with swapping PI parts.
First was the cams, then the Intake, then just a full PI swap that upped compression for cheap power.
There was a guy out in like Minnesota who was porting NPI's for the 4.6 Tbird/Cougar guys that flowed as much as the best ported PI's. Jim was the first name, can't remember the last but he did nice work and his heads were in demand. His ported SVOs were even better. The lack of the intake just didn't let the work shine though.
Ford pulled the plug way to fast with the 2V support. In the beginning we had heads/intake and even the blower but they didn't make enough of them.
Also the 98's were the preferred 2V NPI heads to use in porting. There were improvements in the casting so you could probably find a set for the change in your couch.
Thanks for the history recap, I was there along they way too. Johnny Langton .K.Danner, Nick Mckinny...etc
Only problem is, no one has presented a know how of the potential the heads have in store with just a little port work. The PI head explosion was a simple upgrade over all the stock npi setup, but compresion was the biggest gain with the swap. And yes both heads have different flow characteristics, but can flow equally.
You have those that want proven results simple like a pi swap and those that want to keep what they have and improve on it. Me personally, I just want to have fun building junk yard engines mostly because the price is right. With this said, I figured others would be interested in what it takes to open npi heads up safely.
Only problem is, no one has presented a know how of the potential the heads have in store with just a little port work. The PI head explosion was a simple upgrade over all the stock npi setup, but compresion was the biggest gain with the swap. And yes both heads have different flow characteristics, but can flow equally.
You have those that want proven results simple like a pi swap and those that want to keep what they have and improve on it. Me personally, I just want to have fun building junk yard engines mostly because the price is right. With this said, I figured others would be interested in what it takes to open npi heads up safely.
Thanks for the history recap, I was there along they way too. Johnny Langton .K.Danner, Nick Mckinny...etc
Only problem is, no one has presented a know how of the potential the heads have in store with just a little port work. The PI head explosion was a simple upgrade over all the stock npi setup, but compresion was the biggest gain with the swap. And yes both heads have different flow characteristics, but can flow equally.
The pi intake is still a proven intake for any modular head.
You have those that want proven results simple like a pi swap and those that want to keep what they have and improve on it. Me personally, I just want to have fun building junk yard engines mostly because the price is right. With this said, I figured others would be interested in what it takes to open npi heads up safely.
Only problem is, no one has presented a know how of the potential the heads have in store with just a little port work. The PI head explosion was a simple upgrade over all the stock npi setup, but compresion was the biggest gain with the swap. And yes both heads have different flow characteristics, but can flow equally.
The pi intake is still a proven intake for any modular head.
You have those that want proven results simple like a pi swap and those that want to keep what they have and improve on it. Me personally, I just want to have fun building junk yard engines mostly because the price is right. With this said, I figured others would be interested in what it takes to open npi heads up safely.
How did I double post? Weird
Anyhow, I updated post #25.
Anyhow, I updated post #25.
Here Is a cut a way view of the npi exhaust port. This port is what kills this head! The valveguide bung material, the port runner is smaller than the actual valve seat I.D., and how the whole port/bowl flow together.
If you are willing to port a set of npi heads, starting here first will net the biggest gains. Removing the bung with the stock guide is not recommended. The solution is to leave some bung and knife it while blending the guide to the bung taking out about .200 (iirc)from the guide end. A lot of the bung will be removed by looking at it and I think I have a pic....ill post it soon.
The exhaust port itself is tiny and is not sufficient to flow what the intake port has to offer. Notice the port floor has a lot of meat compared to the roof. Also the exhaust port is the minor difference in all npi head castings, although their is a difference in them. Its the intake port that has the major difference. Yes I just said "all npi heads are NOT the same".
This is a pic of a mildly ported npi exhaust port stock valve size(port work done by a very well known npi guy) . The main focus is the valve guide boss and the amount of guide plus the boss that has been ground/ported out. If you have seen a stock untouched npi exhaust port, you can instantly tell this port will flow considerably more!! Iirc just cutting out the boss while leaving the guide alone will net right at 20cfm more. This exhaust port and the work into it (very simple to do) netted max lift .500 150ish cfm stock npi valve. Replacing the valve and seat with a stock pi size while opening the port to the valve, valve boss removed, bronze valve guide tapered end, under cut stem, multi angle grinds and it gets close to 180cfm at high lift.
A stock compression PI engine(H/C/I) against a stock compression npi ( pi cam/intake) nets within 10rwhp of the pi engine.......I wonder why? Laying the intake valve swirl dam back alittle with some very mild port polish like described in earlier post, porting the exhaust port like described, with flat top pistons (same compression as pi head swap on npi short block) you become a contender in the 300rwhp club! Now add cams!......simple!
Any questions? Feedback? Or is all of this already known?
This pic shows the combustion chamber of the first style npi heads
Here are a few quotes from a known, very well respected modular head porting guru. Im not stalking but thought his reply to a members question about a npi head combustion chamber would be a nice add to this thread.
Yeah Benny might have worked over a couple of sets of these, even got some Ford engineers using them on their personal rides. No quench on this casting, they went to a quench on the replacement opposite the spark plug but it could still use a small quench added on the plug side from the piston top evidence I see. I plan to double quench the race set here and make it like a figure 8 shape, it needs all the compression it can get. Not too many people racing these earlier heads anymore but the intake port actually flows the same with only 2/3 the area of the newer casting. I get 220CFM from that tiny port with very little work. Here is how I modify that swirl dam BTW:
ts called a swirl dam in the Ford world. Remove it completely and you will need to add 6 degrees more spark advance for near zero gain in power. You can lay it back at a 45 to get another 10cfm or so and not lose the spark advance. That particular early casting really wakes up with a simple 3 angle valve job, modifying a set of later intake valves to fit (better back angle), and installing a set of the later cams. I did the cams for the fastest NA motor ever run with those heads, and I am currently putting together a motor that should take that record another second faster (welded chambers, 1.84" SVO intake valves, 3.7" bore, E85 fuel, sheet metal tunnel ram)
Yeah Benny might have worked over a couple of sets of these, even got some Ford engineers using them on their personal rides. No quench on this casting, they went to a quench on the replacement opposite the spark plug but it could still use a small quench added on the plug side from the piston top evidence I see. I plan to double quench the race set here and make it like a figure 8 shape, it needs all the compression it can get. Not too many people racing these earlier heads anymore but the intake port actually flows the same with only 2/3 the area of the newer casting. I get 220CFM from that tiny port with very little work. Here is how I modify that swirl dam BTW:
ts called a swirl dam in the Ford world. Remove it completely and you will need to add 6 degrees more spark advance for near zero gain in power. You can lay it back at a 45 to get another 10cfm or so and not lose the spark advance. That particular early casting really wakes up with a simple 3 angle valve job, modifying a set of later intake valves to fit (better back angle), and installing a set of the later cams. I did the cams for the fastest NA motor ever run with those heads, and I am currently putting together a motor that should take that record another second faster (welded chambers, 1.84" SVO intake valves, 3.7" bore, E85 fuel, sheet metal tunnel ram)
