PORTING HEADS HP GAIN

[moparian]

i would like to know some real hp gains from a ported head s or what gains should we see with this port job ? 12.5 comp 434 afr heads cam lift is 780 net 7400 rpm
200 .300 .400 .500 .600 .700 .800
Int 226 266 308 334 332 332
Exh 126 173 220 246 251 255
int 219 278 324 347 360 360

[mag2555]

Will your intake system support these new flow numbers?
If you want to assume that your intake and Carb are not a restriction and that the added air flow will not kick your port velocity up to high at 7400 rpm then you should make a easy 740 hp @ 100% VE, in fact if you can't hit that hp number something is very wrong!

[ZEOHSIX]

Well.....from the flow figures listed your heads are pretty much done at 0.500" lift and you say your cam is 0.780" lift? There's a whole lot of power to be found in improving high lift flow figures in the heads from what I can see....434 cu/in motor? At least 75-100+ HP should be easily attainable with some decent work depending on what castings you are using....hope they aren't cast iron.

[B Original]

Interested tell us more about the heads and your induction? If they are AFR CNC versions gains will be hard to come by. Although the rpm's and cubic size needs to have 245's opened up to flow a lot more. If you want realistic gains instead of butchering the AFR's I would be looking at a set of 15 or 18 degree heads although that would have you opening the short block up for pistons. I would be looking for 370+ cfm at .900 lift.

Depending on what your other limitations are 245 AFR's may be all you can take advantage of.

[Scotthatch]

It depends on the camshaft too ..... gain per cfm per cyl can be anywhere from .22 to .33 cam dependent if intake and carb support the change

[user-17438]

Interested tell us more about the heads and your induction? If they are AFR CNC versions gains will be hard to come by. Although the rpm's and cubic size needs to have 245's opened up to flow a lot more. If you want realistic gains instead of butchering the AFR's I would be looking at a set of 15 or 18 degree heads although that would have you opening the short block up for pistons. I would be looking for 370+ cfm at .900 lift.

Depending on what your other limitations are 245 AFR's may be all you can take advantage of.

Why do people always say AFR heads are hard to make gains? That's furthest from the truth because every time I slow them down they pick up huge!

I wish you flow guys actually knew what kind of cfm makes what kind of power. Because to tell him to look for 370 is just wrong, if he finds it he probably ruined the head. I shape and size a head, it flows whatever it flows and hits the rpm we want. My ultimate goal is rpm. If you are any good at porting cylinder heads you should already have the feel for what to do as far as shapes and cross sections.

The first limitation on the afr245 is the first thing you see just looking at the intake port.

[Rick360]

Interested tell us more about the heads and your induction? If they are AFR CNC versions gains will be hard to come by. Although the rpm's and cubic size needs to have 245's opened up to flow a lot more. If you want realistic gains instead of butchering the AFR's I would be looking at a set of 15 or 18 degree heads although that would have you opening the short block up for pistons. I would be looking for 370+ cfm at .900 lift.

Depending on what your other limitations are 245 AFR's may be all you can take advantage of.

Why do people always say AFR heads are hard to make gains? That's furthest from the truth because every time I slow them down they pick up huge!

I wish you flow guys actually knew what kind of cfm makes what kind of power. Because to tell him to look for 370 is just wrong, if he finds it he probably ruined the head. I shape and size a head, it flows whatever it flows and hits the rpm we want. My ultimate goal is rpm. If you are any good at porting cylinder heads you should already have the feel for what to do as far as shapes and cross sections.

The first limitation on the afr245 is the first thing you see just looking at the intake port.

whatever works for you doesn't necessarily work for me I guess whether you speeding it down or slowing it up physics is physics to convert BTUs to horsepower you have to have a combination of specific volume of charge that the fuel is sufficiently atomized and necessary the motion to make each horsepower there's no such thing as magic but there is method if what you do works and you don't understand it. just know that the method that get you there doesn't mean that there aren't physics and math that quantifies your results so I'm not disputing you here and I am convinced that you know how to make it work. I just approached it from the opposite direction that you do.

To put it simple terms you need to get a certain amount of water down a river Channel you choose to do it deep and wide and I can make the same water move through a channel it's a wide and deep

B Original (or GVX as you called yourself before you were banned),
You don't understand what he's saying. you think making gains on a flowbench = airflow gains on an engine and it doesn't. AFR heads are designed to FLOW the most CFM/cc of volume which will NOT make the most HP. There is a LOT of power left in an AFR head when you buy it but very little CFM.

Rick
Edit - writing this before he deleted it

[moparian]

sorry guys some of my spacers went missing on the numbers if the engine made 720 before with 334 cfm and now house 360 cfm what hp increase .300.400.500.600.700.800
226 266 308 334 332 332
219 278 324 347 360 360
thats 28 cfm gain around 60 hp in theory the carb and intake cuts 10 cfm of the top

[B Original]

B Original (or GVX as you called yourself before you were banned),
You don't understand what he's saying. you think making gains on a flowbench = airflow gains on an engine and it doesn't. AFR heads are designed to FLOW the most CFM/cc of volume which will NOT make the most HP. There is a LOT of power left in an AFR head when you buy it but very little CFM.

Rick
Edit - writing this before he deleted it

I really don't know what your issue is Rick and I don't care. I'll just keep ignoring you and the other two irritants that frequently pollute post with drama creating trash people looking for information have to read through

I am surprised I didn't give you the ideal if I delete a post seconds after I posted it that maybe I didn't think it was a relevant response to the previous poster? For the most part I agree with MTENGINES post I'm a have some theoretical differences and I agree it's sometimes if you slow things down it can improve the quality of the airflow into the cylinder and after rereading my response I was nitpicking stuff that didn't need to be.

When I read his post the first time it almost sounded like he was saying if you put a restrictor plate on the engine it will make more power but that's not what he was saying so that's why I retracted my post.

[KnightEngines]

I shape and size a head, it flows whatever it flows and hits the rpm we want.

This ^

The flow figures suggest the heads move a lot of air, but not nicely, likely too fast over the turn, that will kill power.
If you fix the air speed, size the pinch right for the motor & get rid of turbulence it may even drop flow on the bench - but it'll make more HP

[moparian]

I shape and size a head, it flows whatever it flows and hits the rpm we want.

This ^

The flow figures suggest the heads move a lot of air, but not nicely, likely too fast over the turn, that will kill power.
If you fix the air speed, size the pinch right for the motor & get rid of turbulence it may even drop flow on the bench - but it'll make more HP

thanks, you do some nice work on the plastic heads

[Scotthatch]

sorry guys some of my spacers went missing on the numbers if the engine made 720 before with 334 cfm and now house 360 cfm what hp increase .300.400.500.600.700.800
226 266 308 334 332 332
219 278 324 347 360 360
thats 28 cfm gain around 60 hp in theory the carb and intake cuts 10 cfm of the top

Yes your general take on this is correct

The debate though sometimes poorly worded is about flow quality .... we talk a lot about flow numbers but just hitting a number does not help if the air at that peak is unstable .... that clean crisp air flow is a hard thing to translate to a message board ... the other part is how a port will behave with a given cam ... I am guessing you are at about a 260 at .050 cam ... with a cam that size the port air flow relates well to HP but as you go up to like 290 things change because the intake valve is closing so late the intake runner and port have to be exactly right to work well.

[moparian]

sorry guys some of my spacers went missing on the numbers if the engine made 720 before with 334 cfm and now house 360 cfm what hp increase .300.400.500.600.700.800
226 266 308 334 332 332
219 278 324 347 360 360
thats 28 cfm gain around 60 hp in theory the carb and intake cuts 10 cfm of the top

Yes your general take on this is correct

The debate though sometimes poorly worded is about flow quality .... we talk a lot about flow numbers but just hitting a number does not help if the air at that peak is unstable .... that clean crisp air flow is a hard thing to translate to a message board ... the other part is how a port will behave with a given cam ... I am guessing you are at about a 260 at .050 cam ... with a cam that size the port air flow relates well to HP but as you go up to like 290 things change because the intake valve is closing so late the intake runner and port have to be exactly right to work well.

cam is 270@050 we may be going back in for a bit more up top intake valve is a 2.150

[KnightEngines]

The bigger the cam the more important the sizing/velocity.
With a late closing intake valve you have to rely on inertia ram to keep the charge moving in the right direction.
If you don't build enough velocity earlier in the intake stroke there will not be enough inertia to keep it moving till the valve is shut, so you'll get reversion which not only reduces cylinder fill but also upsets the port & slows the start of the next intake cycle, so you're hurting fill from both ends of the intake event.
The head can flow like a drain pipe on the bench - that only has a milld relevance to how it'll fill a cylinder at high rpm.

[B Original]

The bigger the cam the more important the sizing/velocity.
With a late closing intake valve you have to rely on inertia ram to keep the charge moving in the right direction.
If you don't build enough velocity earlier in the intake stroke there will not be enough inertia to keep it moving till the valve is shut, so you'll get reversion which not only reduces cylinder fill but also upsets the port & slows the start of the next intake cycle, so you're hurting fill from both ends of the intake event.
The head can flow like a drain pipe on the bench - that only has a milld relevance to how it'll fill a cylinder at high rpm.

Mr Knight you are spot on on everything you say but I like to add if you use a tool like IPO software which gives you data with surprising accuracy like Port energy Port velocity and charge density among other data points can make your flow bench much more relevant to port development.