Wannabriden's D Port Re-Port

Reports of my demise are premature.
Apologies for not continuing the updates but work has continued. Delays during periods of researching, and testing materials, epoxies etc.
Bottom line is the head is complete and has been sent to Garrett. He should have it sometime tomorrow. The testing turned out great and the head looks great as well.

I will begin posting all the information and data as well as review the port design and try to answer any questions during the next week.
Good to be back
Here is a short clip with some pics..
Not what you are waiting for I know but I am trying to lay out the presentation before it is presented.
IF that made any sense,
There is a ton of data which has to be moved from one device to another and not in a friendly manner.
Very shortly I will begin presentingeverything.
So for the moment....

For those that have been following as well as any others:
I think there should be a brief review.

We'll start with styles of porting.

When I first did this in my teens on small block heads I didn't have any real test equipment.
The biggest shop vac I could find and some string.
Combined with a basic understanding of fluid dynamics, it seemed to be enough.
Seat of the pants says it worked great.
I did several for others over the next couple of years.
Then into the Air Force and the rest of life.
Inspired by Jack's thread, once I decided to pursue this
I knew I wanted to be able to gather data at a higher level.
Not cheap even when you DIY, but it's been worth it.
The philosophy hasn't changed since the beginning..
"Do the best you can with what you got"

Style One
"One Size Fits All"
This is the style I utilized in my teens.
Make it go all it can go...

Style Two
"Tuned Port Engine Specific"
The port is design based on an engine's volumetrics.
Those specifications are what determine the volume of air required.
Using formulas from SAE or those derived from them will give the values to target.
Velocity is KING. I like the maximum before going into choke.
I'll discuss this point in the report further as we go.
This rebuild was Tuned Port Engine Specific.

Since the engine specs are required to go further I have provided them here..

Engine Specs - 700cc w/ Shell #1

Intake Valve
Length 4.105
Stem 0.3146" / 7.99mm
Head 1.614" / 41mm
Area = 1319 sq mm / 2.04 sq in

Exhaust Valve
Length 4.030"
Stem 0.3136" - 7.96mm
Head 1.378"- 35mm
Tulip Angle 23
Area = 961 sq mm / 1.49 sq in

Port Runner Length 86mm / 3.38"
Port CC 74cc
Port CSA 1.16"

Port Runner Length 87mm / 3.38
Port CC 75cc
Port CSA 1.15

77.5mm bore (700cc) 2.972"
74mm stroke 2.913"
130mm Rod 5.12"
Rod to Stroke Ratio of 1.756-1

Piston Speed
63 fps / 756 ips

700cc = 40.4 ci

Establishing Targets

The goal is to have all the targets confirmed with inter-related formulas.
Engine formulas are available in many places, including those that complete the calculations once the required parameters are entered.
One should always double check the values.
Always review any unexpected or out or norm findings.
Retest and Verify.

Target One

Required CFM

1) CFM Head Calc.jpg

So here we have a target CFM of 150 CFM for this 700cc w/ a Shell #1 cam.

Target Two

Optimum CSA

2a) CSA   Max RPM  Calc.jpg

We can see that the optimum CSA should be 1.15 sq in.

Target Three

Maximum Port Velocity

There are numerous different standards related to determining a port choke point.
I spent quite some time studying this as well as speaking with other porters for a better understanding.
Ultimately I decided to use a simple determining factor.
When the pitot tube has a greater pressure than the atmosheric test pressure the port is poised for choke.
For these tests that pressure is 24" of water which equates to around 340 fps as a target.

Additionally the port should be as "equalized" as possible. Less variation is better.

I test the port at three different "depths" in mulitiple locations.
I labeled the depths on my charts as 20mm,40mm,60mm.
In reality those are incorrect, the accurate depths are as follows:

15mm - 8 test points

Velocity #1.jpg

35mm - 7 test points

Velocity #2.jpg

55mm - 7 test points

Velocity #3.jpg

Total of 22 test points for Velocity

The targets identified with the previous information based on engine volumetrics:

CFM - 150

CSA - 1.15
Port Velocity - 340 fps

The closer to these values the better.
Consistency of measurement is PARAMOUNT!
Set the standards for your bench and stay within them.
Tighten the standard whenever possible.

What do these targets represent and how important are they?


A N/A engine is basically an air pump and the amount of air that can be moved through the motor is dependent upon the motor specifications.
Falling below this number chokes the motor. Too far above it will reduce port efficiency as well as shift the power curve.
Cammed timing events and power curves must be taken into consideration.

The CSA is sized to achieve the required flow.
Knowing this number eliminates guesswork, hit and misses...

Port Velocity
Port Velocity is by far the most important number here.

Next we look at problems and solutions.....


  • 1c) CFM for 123 VE.jpg
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  • 1) CFM Head Calc.jpg
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A few before and after pics before we get started..

Right Intake Port
Should be obvious which are which...

A few before and after pics before we get started..

Left Exhaust Port
Should be obvious which are which...

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A few before and after pics before we get started..

Right Exhaust Port
Should be obvious which are which...

I thought there would be a bit more work done on the combustion chamber, I have 2 heads both came with just about the same in the combustion chamber with all the edges smoothed right out.
I thought there would be a bit more work done on the combustion chamber, I have 2 heads both came with just about the same in the combustion chamber with all the edges smoothed right out.
Hey Jay...
Really a port repair for Garrett. I did a bunch of extra stuff.
I did smooth out the valve shrouding on the junk head provided by gggGary.
The testing from that showed little variation at these specs. with a .400 lift cam.
I was able to achieve the targets without having to do more than a slight smoothing of sharp edges,
so that is where I left it, other than a semi-polish.
Testing did show a potential for "vaning" the air flow to create more "swirl".
Something I may chase later.
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Here are the CFM numbers for the head.
I tried to make the chart as easy to read as possible.
Left on the left and right on the right.
Measurements for lifts at .050 increments.
The full tenth lifts are highlighted in blue. I call them the "Top 4".
Total CFM is adding all 8 measurements once each.
RT means "Round Trip"; which adds all the CFM for each increment for a full valve lifting cycle.
Notice on the right side the "% Difference" which is the difference in percentage of increase from smaller to larger.
These percentages are for each lift increment. The CFM Difference shows how many CFM those percentages represent.
The red circle in the lower right shows the avg CFM/sq Inch across these 8 increments. Notice that number... 114 avg.
We'll talk about it soon.
The % Difference between the Total CFM for the 2 ports is .002%
The % Difference between the Top 4 RT CFM for the 2 ports is .004%
The % Difference between the All 8 RT CFM for the 2 ports is .005%

The ports arrive at from slightly different directions.
One is slightly better at the lower lifts and vice versa.
Still the numbers are incredibly tight.
I should remind everyone that the plus or minus on this bench is 1% to 2% depending on how far from the calibration points the air is measured. That should be considered within the margin of error.
BTW.. I took video of these tests and will post some snippets along with the corresponding data sheets sometime soon.

Remember that we have establishished a CFM target of 150 CFM
Here you go....

Combo CFM.jpg
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One of the most important factors is velocity. The key element.
The target is 340 fps as explained above.
A few points to make regarding the charts.
Keep in mind that the left and right ports are NOT identical, they are MIRRORED.
In the top chart each test point is color coded to match the comparable test point for the opposite port.
Those measurements are compared and the differences are as noted.
Also the % shown for the Port Avg Velocity in the blue circle lower right in the velocity charts
is the percentage of velocity flowed compared to the targeted velocity od 340fps

The Port Balance Velocity Chart at the bottom shows the variation between each of the color coded pairs.
As an example: if the value reads R-99; that is understood to mean that the Right Port flowed 99% of what the Left Port flowed.
Hopefully the charts are mostly self explanatory but I am always happy to answer questions.
The difference between the left and the right at all three testing depths is 1% (actually less).
The charts....

@ 15mm Deep

D45F Velociity Trip 15mm.jpg
@ 35mm Deep

D45F Velociity Trip 35mm.jpg

@ 55mm Deep

D45F Velociity Trip 55mm.jpg
A couple of quick notes before I get into port design...
Waaaay back for those that have followed from the beginning; you may recall me discussing the EFFICIENCY of the port/
I went into how it is important in determining how "active" a port is.
This may be the ONE measurement that is as important as the velocity.
As a reminder it is pretty simple, how many CFM/CSA"= CFM per sq inch.
You may recall the targets (there's that word again) established by Superflow (146) and the SAE (137) as being the maximum. I lean to SAE.
Their standard was a correction to the Superflow model.

Street 116
Street/Strip 126
Max 137

This head flowed 153 CFM. Has a CSA of 1.15 sq inches.
153/1.15 =
133 CFM/inch
That is pretty darn efficient. I am very pleased.
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As we discussed port efficiency above I am attaching a video showing the final flowball test.
In a flowball video before I explained how this works.
Basically we want the smallest flowball to affect the flow throughout the port.
That would mean that the fluid would rise wherever the flowball is placed in the port.
It is important to eliminate all dead zones.
I was able to get fully active ports using the second smallest ball.
Although not the ultimate target, this is exceptional.
I apologize in advance for the light colored water, The red faded.
I should have added some dye before testing. I could see it. Hopefully you can as well.
The audio is rather poor also.
The focus should be on the rising and lowering of the water in the left tube as the flowball is placed into the port.
This test is a visual example of the port's efficiency as indicated in the above posting.
Part of the verification cross testing I talk about.

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Smoke test results.
Nice and tight beams center focused targeting the stem or just to it's side. No crossover or anything remotely close. Sweeeet!

D45F R Smoke Testingb.jpg
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D45F ??? WTF """"????
D- It was a D Port
45- 45* Valve Angle
F- The 6th rendition of the Final shaping.

So it's simply a designation used by me to track the head's build status.
F can also symbolize the Final Status of the build, The Final rendition.
Of course, even more obvious....
F stands for FAST..... ;)
Valve Dispersion Testing

The valve dispersion testing idicating flow areas over the valve.
Keep in mind that the valve /seat and throat area control the flow until approximately .230 lift when the port takes over.
Another key to keep in mind is that the ports and chambers are mirrors of one another.

The side by side comparisons of the valve's dispersion percentages at both .10 and .20 lift (under valve control)
indicate there is an imbalance. We are looking big picture not detailed minute differences. Basic flow patterns only.
Knowing that the ports and chambers are mirrored one would expect that the flows should reflect that.
At these lower lifts it is clear the left port is flowing much heavier across the plug side of the valve.
Interestingly, the right port flows opposite with the vast volume of flow being carried across the inside portion of the valve.
The difference, is not as vast as it appears from the numbers themselves.

Ultimately the volume of air moving at these lifts, makes the imbalance seem insignificant.
Most likely cause is a slight variation in the treatment of the valve shrouding areas (ridges) surrounding the valves.
Wherever the imbalance is we know it is related to the valve area because it is in control at those lifts.
I pursued this no further although I may do further investigations as I continue to improve.
I firmly believe that this imperfection will have negligible effect on the performance of the head.
Indeed it is one that few even bother to discover.

In the examples below, the numbers to see are the big blue sets.
The side by side numbers are just that.
The percentage of flow across the left half of the valve top and the same for the right as well.
The "division problem" number set show the percentage of flow across the LST half of the valve and vice versa.
It is expected that the LST should flow more than the SST.
Remember Rule #2 of the 5 Golden Rules of Porting???
Let the air go where the air wants to go.
Nuff said.

@ .10

Combo Valve DP 10.jpg

@ .20

Combo Valve DP 20.jpg

Now as we get into the tuned port controlled lifts one can see the balance.
Mapping the Valve DP at the .30 and .40 lift points present yet another example of how balanced these ports are.
Not balanced as in each and every "pie slice" is precisely the same.
Balanced as in each and every zone is balanced with it's counterpart.
Different testing verifying the same information.

@ .30

Combo Valve DP 30.jpg


Combo Valve DP 40.jpg