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107", JE pistons, 10.75 cr, S&S 640, ported heads, 1.98 int, 1.61 ex, 54mm TB, 4.9 inj.
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Discussion Starter · #1 ·
So I'm brand new, learning about porting, trying to absorb as much info as I can before porting my first set of heads. I would like to know if there's any truth to have max and min wind speed through the intake while flow benching a head. So as you port you check on it on the bench to make sure you're going in the right direction. You're not just trying to increase your cfm's but regulating air velocity going through the port which if done correctly will give you the cfm you need.
I read a small article the other day that said velocity should not be more than 285-310 fps at its tightest point and that the rest should flow between 246-268 fps. Any Pros here that can confirm if this is true or not and maybe go into more detail on this?
 

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107", JE pistons, 10.75 cr, S&S 640, ported heads, 1.98 int, 1.61 ex, 54mm TB, 4.9 inj.
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Discussion Starter · #2 ·
Here's a link to what I read.
 

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What looks EZ,.... is trespassing into a world where the amateur will fail at first guaranteed!.
Where angels dare not to tread as they say.
Spend a few hours watching David Vizard
Reading joe Mondello

Then go read Smoky Unick.
These reads are absolutes in prep work.
And you are going to get smarter, ESP, IF you buy some classes from David.

You are dealing with speeds of 600 MPH -rocket science on a miniature scale
Flow tables- like dynos, and leak dwn testers are only as good as the operators.
Some people are just a carnival act and operators deceiving the stupid.
I doubt that you will ever see a real Porter on here divulging secrets he has spent years learning.
There are some things that can be done in any backyard but you will need some sort of hard seat grinder and valve facer.
The old Sioux setups work just fine and can be found under a grand.
Mondello sells cutters carried by Goodson.
Dont get the intake and exhaust cutters mixed up.
Porche ports can be copied to some degree if you know nothing (the boat bow)
Tulip valves and angles not radius on the intakes.
Once you start dwn the slippery slope to speed you are also entering the word **linear.
It is a particular ailment for us few people that live on the edge of reality.
**Everything you do to a stock Harley engine to move it closer to one to one and more, is a direct correlation to TBO becoming shorter and shorter.
People wil tell you anything and you will belive everything if you are naive.
 
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With words of encouragement here,
Certainly, no dis intended-
Pursue this if you like the idea of escaping the norms .
Any crude caveman shop can bolt on cubes and get one to one out of it @ about 10 to one CR
No challenge there, no magic required
But there is no college for porting. (maybe aeronautics)
What looks good for the eye, turns to crap in the wind tunnels.
One would think curves are great with nice slow radii.
This turns out not so true unless moving slow.
Look at the real modern jet fighters..It is not just about radar albeit that is what we are told.
One can learn, steal, spy, and for ideas. The big companies do it all the time.
We can attend some short courses and get the ideas. (David V. again)
But the caveat is- there are some other things that come along with not just port shape and velocity
It is the whole pic of stroke and cam, rod ratio, that has to be addressed..
Squish. etc etc etc
One thing changes the other.
Strictly Harley?
A lot has been done so you do not have to reinvent the wheel, just learn where the spokes already are.
 
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107", JE pistons, 10.75 cr, S&S 640, ported heads, 1.98 int, 1.61 ex, 54mm TB, 4.9 inj.
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Discussion Starter · #8 ·
Yeah, I get I will be going through twin cam heads learning this. Good things they're cheap to buy used.
Thanks for the links and all, I'll check them out with all the others I have to read and watch.
 

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There are two styles of Twink heads, one with smaller valves .
I have found setting the seats toward the bottom of the valve, on the narrow side, not a mile wide like HD dictates will help a lot.
As I said -A slippery slope to quicker TBO with ever-faster improvement.
You are not going fast and a lot of miles, at least not on a Harley. Not on the other side of one-to-one.
Then there is 45 deg seats which again is the best for longevity -steeper is a lot better.
 

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After you fix the hot spots and get the flow velocity equalized are the heads going to make more power? Are the heads actually the constraint that is in the way of added power and torque to begin with?
A big YMMV!
I have had heads brought to me that owners did their very best to port and they ask "how do they look". I respond, "how do they measure and how do they test"? When we test a stock head first then theirs often times they are very disappointed that theirs flow less or have issues. Math and a flow bench is essential to develop well functioning intake ports and in my opinion experience and proper sizing is a better ruler for exhausts. A lot of emphasis in the planning stages goes to port geometry and valve sizes based on engine demand. Porting a head out of the context of the demand is useless. How far do you open the barn door? After the head is opened up and local velocities OK how does the sizing related to the demand? An optimized port based on the factory starting casting is just optimized for a certain engine size and specification and not necessarily yours.
I strongly recommend, if you are serious, you buy or build a flow bench that is capable of 600 cfm at 60" H2o and equip it with Performance trends hardware and software. This has tools to plan the work before grinding anything. Best book I suggest is Engine Airflow, ISBN 978-1-55788-537-1. Software, Performance Trends and PipeMax. Just a starting point, this is a large commitment if you are serious. Otherwise send the heads out or just pocket port them and roll the dice.
Best of luck.
 

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107", JE pistons, 10.75 cr, S&S 640, ported heads, 1.98 int, 1.61 ex, 54mm TB, 4.9 inj.
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Discussion Starter · #12 ·
After you fix the hot spots and get the flow velocity equalized are the heads going to make more power? Are the heads actually the constraint that is in the way of added power and torque to begin with?
A big YMMV!
I have had heads brought to me that owners did their very best to port and they ask "how do they look". I respond, "how do they measure and how do they test"? When we test a stock head first then theirs often times they are very disappointed that theirs flow less or have issues. Math and a flow bench is essential to develop well functioning intake ports and in my opinion experience and proper sizing is a better ruler for exhausts. A lot of emphasis in the planning stages goes to port geometry and valve sizes based on engine demand. Porting a head out of the context of the demand is useless. How far do you open the barn door? After the head is opened up and local velocities OK how does the sizing related to the demand? An optimized port based on the factory starting casting is just optimized for a certain engine size and specification and not necessarily yours.
I strongly recommend, if you are serious, you buy or build a flow bench that is capable of 600 cfm at 60" H2o and equip it with Performance trends hardware and software. This has tools to plan the work before grinding anything. Best book I suggest is Engine Airflow, ISBN 978-1-55788-537-1. Software, Performance Trends and PipeMax. Just a starting point, this is a large commitment if you are serious. Otherwise send the heads out or just pocket port them and roll the dice.
Best of luck.
I have a shop where I had the heads done for my dyna at last Summer to use. The machinist that did them past away at Xmas. His son has taken over the shop and is missing a little knowledge that his dad didn't have a chance to pass on....kinda why I'm wanting to know about velocity. He does have a Super flow 1020 I can use.
 

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Discussion Starter · #13 ·
There are two styles of Twink heads, one with smaller valves .
I have found setting the seats toward the bottom of the valve, on the narrow side, not a mile wide like HD dictates will help a lot.
As I said -A slippery slope to quicker TBO with ever-faster improvement.
You are not going fast and a lot of miles, at least not on a Harley. Not on the other side of one-to-one.
Then there is 45 deg seats which again is the best for longevity -steeper is a lot better.
Yeah the 88ci twin cam and the newer gen starting at the 96ci with the 7mm valves.
You want the throat opened up 89-90% of your intake valve size and 85%ish of your exhaust valve correct? 3...4 angle on intake 5 angle on exhaust? Obviously match up the intake to the manifold.
Do you want velocity as even as you can get it across the port? Cause the velocity sure likes to be faster at the short turn.
 

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The caveat is a steeper seat and the throat ratio can be a puff larger, generically.
For sure I was thinking this thread would assemble a lot more interest, as the Op opened with is a measure of
sanity and craziness all at once in a good way!
On the Porsche stuff, we do as much as 93 % but the runners are a lot longer and a different animal.
Twinks all though just like any Harley's head are completely foreign to me .
No experience.
Evo, yea I use velcro for fasteners now.
But I will guess raised ports on a twink would do a lot too?
 

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Do you want velocity as even as you can get it across the port? Cause the velocity sure likes to be faster at the short turn.

Yes! Too fast off the ramp will go across and short the roof airflow. You will hear it and see it on the flow test, flow reduces with advancement of the valve opening.

Don't get too wrapped up in the grass blades as far as recipes. One size does not fit all. You will have to buy some cutting form tools, assuming you have a seat and guide machine or a milling machine with roll-over fixture and proper ball head tooling, and flow test to determine what works best. I would start with the basics 30/45/60 intake and similar exhaust then try others from there. Goodson offers good support and suggestions of a general nature not specific to HD. Once you read Harold Bettes book you will have most questions answered at least a start. PipeMax software will give you a target CSA to shoot for and a port mold will help you decide what needs to change, plus the use of flow balls and velocity pitots. Remember you have a different requirement (demand) and a starting canvas, head version and constraints due to factory castings, every time. Core shift is a factor also. Some of the basics carry over to all heads. Remember intakes must work best air in and exhaust airflow out. Test backwards and you will be amazed how well that swoopy exhaust port works in reverse. That needs to be fixed. I don't get into all the nuances on the net or by PM. Plus I am not the end all subject matter expert.
Another forum I suggest is speedtalk.com, the car guys on that forum are especially helpful and knowledgeable.
 

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107", JE pistons, 10.75 cr, S&S 640, ported heads, 1.98 int, 1.61 ex, 54mm TB, 4.9 inj.
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Discussion Starter · #16 ·
Do you want velocity as even as you can get it across the port? Cause the velocity sure likes to be faster at the short turn.

Yes! Too fast off the ramp will go across and short the roof airflow. You will hear it and see it on the flow test, flow reduces with advancement of the valve opening.

Don't get too wrapped up in the grass blades as far as recipes. One size does not fit all. You will have to buy some cutting form tools, assuming you have a seat and guide machine or a milling machine with roll-over fixture and proper ball head tooling, and flow test to determine what works best. I would start with the basics 30/45/60 intake and similar exhaust then try others from there. Goodson offers good support and suggestions of a general nature not specific to HD. Once you read Harold Bettes book you will have most questions answered at least a start. PipeMax software will give you a target CSA to shoot for and a port mold will help you decide what needs to change, plus the use of flow balls and velocity pitots. Remember you have a different requirement (demand) and a starting canvas, head version and constraints due to factory castings, every time. Core shift is a factor also. Some of the basics carry over to all heads. Remember intakes must work best air in and exhaust airflow out. Test backwards and you will be amazed how well that swoopy exhaust port works in reverse. That needs to be fixed. I don't get into all the nuances on the net or by PM. Plus I am not the end all subject matter expert.
Another forum I suggest is speedtalk.com, the car guys on that forum are especially helpful and knowledgeable.
Thanks Don!
What is your take on too much velocity and the right amount of velocity? If you have too much will it rob you of cfm but too little and the mixture doesn't stay atomized?
 

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Discussion Starter · #17 ·
The caveat is a steeper seat and the throat ratio can be a puff larger, generically.
For sure I was thinking this thread would assemble a lot more interest, as the Op opened with is a measure of
sanity and craziness all at once in a good way!
On the Porsche stuff, we do as much as 93 % but the runners are a lot longer and a different animal.
Twinks all though just like any Harley's head are completely foreign to me .
No experience.
Evo, yea I use velcro for fasteners now.
But I will guess raised ports on a twink would do a lot too?
I thought there would be more action on this subject also. But I'm getting some good info from those who are. Thanks
93% eh. What allows to be able to go over like that...larger displacement, higher compression?
 

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steeper seats.
The throat ratio is very very fussy.
And learn to love reversion.
The Rembrandt worth owning, a halo is worth watching!
The engine paints its own performance !!
Artwork in action.
 

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I thought there would be more action on this subject also. But I'm getting some good info from those who are. Thanks
93% eh. What allows to be able to go over like that...larger displacement, higher compression?
Mate most have done there porting to get the results needed and then use CNC machines for the exact profile every job. Plus some porters dont want to give up their years of testing
 

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Can you blame them?
However, port ratios and multi-valve angles are discussed quite regularly.
The super-secret stuff is not ever mentioned.
Moving ports-Changing valve locations, etc are never ever brought up.
Again, Can we blame them?
 
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