Wannabriden's D Port Re-Port

Hey guys...
Some more done today.
No video as it would just be repetitive from yesterday. Hopefully you all realize I am not fudging anything whatsoever. It is what it is. However I did video it if someoneveeally wants to see it. I am documenting everything. Just saving your ears đź‘Ť
So today I finished testing the right intake on the stock head as part of my plan to completely spec the head. I am focused on the intake side at the moment so the exhaust side will wait. I also managed to flow the left side intake of Garrett's D Port head. I think those of you following this will find the results interesting.

I have found that it can be tricky adjusting to get 28" with small valve openings but gets easier as the valve opens up.
Absolutely Signal. I am going to be modifying my setup by pigtailing my dimmer switch, extending it to mount next to my u shaped manometer. Easier for me to adjust and correct. Errors there will be reflected. I am also considering adding a purge valve to help balance the bounce, some of which may be influenced by the motor fluctuating through the dimmer switch. I will have to see, but would definitely like to see that area improve .

Thank you for taking the time to get your flow bench up and running, it looks great. The numbers I gave were off a calibrated superflow
Jack I am thankful to you for inspiring me to do this. I know that I couldn't do this endeavor without the aid of the flowbench. Your ability and knowledge is clearly evident considering your results were accomplished without the ability to test as you modified the ports. I am hoping that once that phase starts you will have input based on what we uncover / discover in our exploration. Your reputation is stellar and well earned.
Last edited:
When I made this posting originally it contained erroneous numbers regarding Jack's D Port head.
In an effort to eliminate the possibility of passing incorrect information to others that may be reading this thread I have decided to delete the parts of the posting that could cause confusion.
I have replaced that information with the correct specifications provided by Jack below and available in his D Port thread referenced in the initial posting.
I apologize for the error and hope it didn't cause too much confusion. It is my desire for this thread to be as accurate as possible. I am grateful to all that help me to keep it as such

The D port when done correctly will flow big down low and right through the whole flow curve with increased velocity.
I believe you will like the attachments below.
I made 4 different charts.

Chart 1 is simply the stock head's numbers from the left yesterday and the right today. Nothing surprising and clisely matched. I included the percentage of increase for each of the increments.

Chart 2 compares the stock head left port with Garrett's D Port left side. The incremental increases are included as well here, however the numbers to look at are the PERCENTAGE OF GAINS in the center column. I will also point out the 10% gain in total CFM.

Chart 3 compares the stock head to Jack's D Port using the numbers he posted (which I reposted above).
Because my calibrated flowbench flowed so closely to the calibrated flowbench his head was tested on; I felt it reasonable to include his numbers here for comparison.
Again the incremental increase percentages are noted, however as before it is about the percentage of difference in the center column.

Garrett's D Port percentage of difference goes from a low of 7% at .2 lift to 12% at the highest lift. A variance of only 5% across the entire spectrum with the highest percentage at the highest flow.

Jack's D Port's percentage of difference goes from a low of 7% also at .2 lift to a high of 25% at .3 lift. A variance of 18% across the entire spectrum with the bulk of the percentage occurring in the .3 to .48 range. I will also point out that the head showed acwhopping 17% gain in the total CFMs over the stock head.

The statement made in the quote above is exemplified in these test results.
It is all about the EXECUTION.

Chart 4 is a direct comparison of Garrett's D Port and Jack's D Port.
The CFMs are not being compared here whatsoever. Again it is all about the PERCENTAGES.
The only Two comparisons are the percentage of difference and total CFM flowed.
Garrett's head was modified by Hugh in an effort to copy Jack's port design. It should be no surprise that the numbers are similar and have the same basic flow trends (at least in regards to the CFM numbers). There is a difference in the execution of the design and that is reflected on the small yet steady increased gains shown in Jack's head's flow.
These gains though small add up to a significant amount; in this case a 6% increase above the D Port "copy" which itself was a solid 10% more total CFMs than the stock head.

In closing...
The delamination issues aside, this should show others that there are significant gains which can be made utilizing this design; even if not particularly experienced or talented at such an endeavour if one follows the design parameters Jack has developed.

More to come..
May be a couple of days. Wife has an appointment first thing in the morning and I have my yearly physical Tuesday afternoon.
But I'm loving my shop time soooo.
Stay tuned.


  • 20230402_204426.jpg
    210.9 KB · Views: 77
  • 20230402_204510.jpg
    201.7 KB · Views: 76
  • 20230403_153842.jpg
    201.3 KB · Views: 69
  • 20230403_154800.jpg
    216.4 KB · Views: 79
Last edited:
You need to go back to where I reflowed the D port to correct the left port flow percentage
Left port flowed.... 87.84-125.28-192.44-215.08-225.........Right port flow..... 90-127.27-195.27-212.25-224.25
flow lifts from 100 to 480. There's been some confusion here and I will correct it later today
Last edited:
The flow numbers you used for references were from a stock head I ported and the intake port( bowl) was ported rather oversized with
a tricked-out valve job that had great gains but came at the cost of turbulence. The goal of D porting was to limit (Cut back) on low lift
and bias the flow to come on stronger right around 250 to 300 lift to max lift where a stock ported port would begin stalling right around 400.
In comparison to a stock port,a D-Port is leaps and bounds better in the mid to high lift ranges where the valve remains open longer packing
the cylinders.
I edited the post above in question to remove the incorrect information and replaced it with the corrected numbers provided. I am hopefull this will eliminate any confusion.

Thanks for clarification Jack.
I know didn’t go back and grab the updated numbers. I had the pic from the data sheet you posted and used it. I knew it had the stock head numbers and simply out of curiosity I wanted to compare those with my stock head numbers. I was admittedly shocked they were so close.
I guess that once I flowed the D Port, I made the mistake of assuming the modified specs on that flowsheet were your D Port and decided to dive in. Apparently I hit my head on the bottom of the pool. Those comparisons were probably overreaching but I found it interesting.

I am going to being doing a couple of bench modifications today just to make it easier for me as I dial in my process.

I always appreciate any and all comments regarding corrections for errors from you or any other members should they notice something.
Last edited:
I need to make a correction also those D/P last flow numbers were from the head I sent to Germany but had to rework the shorturn
to balance the flow %. in regards to #s posted in your fourth example
Here are some numbers from the first D/P welded-up combustion chamber with shrouded valves 91-132-170-185-198
After going back in to rework the entire port........................................................................................80-119-181-201-205
Project update..
First I would like to say that my wife's eye appointment Monday went well. Doctor said the eye is healing well. Scheduled us for next Monday with some medication changes.
She still hasn't been doing well as she isn't seeing the results through her vision. That is until today.
Her vision increased significantly today and it lifted her spirits significantly. It should continue getting better and the Doctor has yet to begin addressing the vision aspect as his focus has been on the healing. Sooo good news.

My yearly physical went well all my numbers look great. No issues at all. I'm not on any medications and that hasn't changed yet.

Made some midifications to the bench along with getting a few other things done.

1. Moved my dimmer switch which controls 2 motors next to the U-shaped manometer. Much much easier to correct any drifting of the vacuum pressure when testing.

2. Upgraded my valve opening fixture with larger threaded bolts and added rounded heads to interface the valve stems. This works so much easier. I feel the accuracy has been increaded.

3. Added some powerstrips..
One near the settling chamber and one on my rolling island style work table. Less dragging cords for power when needed.

4. Also cut some lighter springs for the valves when testing but it remains to be seen if they will be sucked open once the pressures are felt.

5. Tested some "Totally Awesome" for cleaning aluminum. First tried it on the junk head sent by gggGary. I pressure washed the entire head after it was removed after 12 hours. There is a clear difference between the soaked side versus the side not treated with the "Awesome". Not sure how well it shows in the pics but it is obvious in person. Wanting to see how well it still worked I used it on a sidecover which was extremely filthy. For this attempt I made my own "Hot Tank". You can see the video here.
The video shows the result after one hour. I then flipped it to soak the other side also for an hour. Pic shows it after it was removed. It was darkened, some discoloration, which I feel sure can be polished back to bright. More experimenting with this upcoming.
I will be vapor blasting the junk head once my new nozzle arrives so I can make sure it is clean as I prepare to open it up and also begin testing some welding techniques on it...

6. Perhaps the most important thing accomplished this week has been the naming of the flowbench. Katrina came in a close second.

Tomorrow I will be completing the testing on the D Port. This will include the CFMs of course as well as the following:

A. Flow ball testing each "Slice" with the 9 point system going in increments of 10mm deep on each slice for a total of 60mm deep or to the SSR. Specifically will be measuring for high turbulence as well as dead spots and rating those findings for reference. This will be explained in the video when I perform these tests.

B. Velocity testing with a probe in the intake port.
This well be accomplished using the same 9 point "Slices".

C. Velocity testing at the intake side of the valve clocked in different positions.

D. Smoke testing in an effort to detect "Swirl"
I will be using a boroscope to video these tests.

Upon gathering the above data I will begin removing the epoxy from Garrett's D Port in preparation for the Re-Port.

Hopefully all goes smooth.
Pics are attached.
Video of the "Hot Tank" will be added once youtube uploads it.



  • 20230406_175023.jpg
    161.6 KB · Views: 57
  • 20230406_175030.jpg
    150.2 KB · Views: 55
  • 20230406_181157.jpg
    180.9 KB · Views: 55
  • Screenshot_20230406_174342_Chrome~2.jpg
    40.6 KB · Views: 56
  • 20230406_174736.jpg
    200.5 KB · Views: 59
  • 20230406_174653.jpg
    151.9 KB · Views: 57
  • 20230406_181303.jpg
    189.4 KB · Views: 60
Last edited:

Finished testing the D Port last Friday excepting the chamber smoke swirl.
A LOT of data. Took a couple of days away to celebrate Easter with the family.
Wife had a doctor appointment today and it went well. Still a ways to go.
Made a teaser video with some excerpts.
Going to take a minute to digest this and present it in a way that is easy to understand.

The video shows some flow balls...
What you don't see is shots of the manometer which works hand in hand with the flow balls.
There wll be a video on this subject alone. Much to be learned by thiat section alone.
Obviously the "flags" make an appearance as well.
The real work is farther down the port but this tease gives a hint.

The smoke factor is huge and I unfortunately came up a bit short with my smoke generator.
My original idea was incense which isn't nearly enough.
Then I thought about a "Power Hitter" which I made from a ketchup bottle.
It is what was used in this video. Performed ok in the port itself.
Unfortunately not enough smoke for the chamber swirl I'm wanting to see.
I'm going to have to Tim Taylor the latest attempt which works but needs amped up.
I am betting success tomorrow on that front.
In the video... The first smoke test is at .2 and you can see the smoke just trying to break away from the SSR.
The next shot is at .4 and it is totally overshot. With more smoke we will be able to see exactly how well it is turn around the valve.
You can see the clear shot from inside the cylinder looking up at the valve. It is wide open but the smoke is not thick enough.

Velocity probe... Identifying the fastest parts of the port.
Extremely important. I am doing this with a simple tube that will give me the depression drop.
The deeper the depression the faster the air. There is a maximum speed that you should target in a port.
That is about .55 mach. or around 600 fps. Most ports work well in the 350-400fps range.
There is a formula to determine the optimum for your engine. We'll get into that as well.
Using a single tube measuring depression I can identify the fastest parts of the port but not the actual speed.
I have a pitot tube coming which will allow me to measure the air speed within the port. Perhaps 2 weeks away.
Not critical for mapping this head but will want it when I rebuild it.

Know I'm missing some things but this is a slice. I expect the videos to start dropping at the end of the week,
The video....


What are they and what do they do?
They are used to help identify air flow through a port when mapping that port.
Combined with the physical mapping (measurements) of the port, air flow mapping gives a better understanding of what is happening.
Flowballs are a restriction placed within the port to upset air flow.
It can also give indications of directional movement as the air buffets the ball.

Flowballs are used with a manometer which indicate the amount of restriction.
Higher restriction means that the flowball is blocking air moving at a higher velocity. The smaller flowballs are used to define smaller areas. Areas that are too violent could potentially be moving too much air. Those areas may need to be opened up to slow the flow. Other areas show only a little movement on the manometer. Modifications in those areas will often yield little return.
Lastly some areas will show no movement. These "dead" areas are ideal spots for fuel drop out. They are a great candidate to be filled.

The windy day example.
On a really windy day, where are the leaves? In the AIR!
When the wind stops the leaves fall to the ground.
Where are the leaves located around your house?
Where the wind DOESN'T blow!
Just like the leaves, fuel collects in these dead areas.
Those areas need to be brought to life.

When using the flowball, you are feeling the turbulence (or lack of) with your fingers. You will hear a pitch change. In the video I call it a whistle; however it isn't really a whistle so much as being a change in intensity and pitch of the air movement. It may be a bit difficult to hear on the video but it is quite obvious live. Such pitch changes should coincide with movement on the manometer.

The ideal port?
That would be a port where the flowball will affect the flow at any point and any position within the port. This would indicate that all the surfaces are working.
That is the target. That is the goal. What size ball? The SMALLEST ball.
The smaller the ball that affects the port at all points and positions; the
better the port is performing.

Video is a bit long and a bit loud.
It is repetitive as the tests are conducted again and again.
I wanted to show all the testing. The stock head testing will be following soon for comparisons as well as establishing a baseline for future port modifications.

It is obvious from these test results that there is MUCH work and improvement required to optimize this particular D Port. We'll get into those thoughts soon.

Last edited:
More numbers..

One of the objectives in porting is to maximize the use of the entire valve moving air into the chamber. At higher speeds the air will detach from the Short Side Radius (SSR), skipping across to the Long Side (LS). To much velocity creates a log jam with all the air trying to cram into a smaller percentage of the valve. This is when the port starts choking.

The valve, valve seat, and throat area represent the greatest restriction within the port. I use a valve that has a hole opening on the port side connected through a hose to the differential pressure meter. The valve can be clocked in any position to read pressures across the top of the valve at whichever position is chosen. See the attached pics.

I tested at the SSR, the Inside wall, the LS, as well as the spark plug wall. The findings are attached. All testing was done at 28" water depression. The tests were run at .1,.2,.3, 4 and ,45 in each of the 4 chosen positions. The readings were recorded. It's important to note that the reading are taken in inches of water. They are NOT converted to CFM or FPS. Those conversions are irrelevant. The greater the pressure drop the greater the speed and volume of air. We are only concerned with the relative values between the 4 points chosen (one can choose as many as they desire) for testing. See the attached chart.

You will see that the SSR only flowed about 14% across all lifts. Slightly higher at the 2 lowest lifts. The LS flowed about 30% of the combined air across the 4 points with the 2 sides each around 28%.

I have yet to fully test the stock head.
I think it will be interesting to compare once I do.
I have started assembly of my grinding stand and will begin removing the epoxy from this D Port at the beginning of the week.
I will be vapor blasting the junk head to complete cleaning it in order to grind it out and test it with some various welding / brazing techniques.
This next week will see the stock head fully tested and the real work begin as the grinding starts and the testing of the filling material takes center stage.


  • 20230414_160536.jpg
    239.2 KB · Views: 58
  • 20230414_160623.jpg
    260.8 KB · Views: 59
  • 20230414_195344.jpg
    243.5 KB · Views: 59
Taking a look at the delamination issues with Garrett's D Port built by Hugh.
I think it is worth noting that there are no apparent issues with any delamination of the epoxy on the floor.
All the delamination occurs on the side walls. There was no anchoring used in the floor of the port.
My understanding is the engine appeared to have been run long and hard.
It's important to understand that the intake's were never port matched for the new D Shape;
thus exposing the epoxied floor's leading edge to what had to unquestionably have been extremely turbulent air.
Yet no delamination anywhere on the floor. Also some discussion regarding the radii of the lower corners.
All the epoxy is coming out.... Get your grind on.

Post # 74 Great video content with a clear explanation. Thank you for taking the time to drag the rest of us up to speed. I watch a lot of David Vizard’s videos and have one of his books and they are great, but they are all about large car motors. Your video is about XS 650’s and couldn’t be better suited to your audience here.

Jack went to some effort to weld and fill the port walls to remove the bulges by the stud holes. It will be interesting to see if your tests show if it would be more beneficial to leave or even reshape them.

Post #75
Very interesting showing the areas of delamination are where the walls were filled. I have a 9mm floor wall radius at present as you said, I will test this out and then reshape and test with larger radius. The cut radius will in effect be even less when the floor is raised 3 to 4mm. This will take me some time as this is one of many projects on the go.

I also note that the head you are repairing has less of the floor removed than Jack took out on the head that went to Germany. Possibly the head you are working on has a smaller port volume.
Keep up the good work watching with interest.
The epoxy has been removed from the D Port.
I will begin modeling the port with clay while simultaneously testing until a design is determined.
I will also begin working with the junk head (Thanks gggGary) for testing.
I will be using a dual path testing on the junk head.
One path will revolve around port modification and design opening the port to it's limits.
The other path will be centered on welding techniques (brazing actually).
Additionally I will begin "pocket porting" my stock head for comparison testing with the already established baseline on that head.
Very basic port casting cleanup and valve work that can be accomplished by many members.
We will be determining how effective these modifications are.
Fun is just getting started...

Since some of the changes I am evaluating may be relatively small individually, I have been attempting to tighten down the accuracy in the bench's calibration. 2% is pretty good but it's too much, it can be better. There are a few things I have identified and have had success with. Mostly procedures where I have been the variable/issue. Final calibrations tomorrow.
I also ordered a second calibration plate to verify the accuracy and I think it should be arriving tomorrow as well.

I'll explain the updated procedures in the next video posting. Other aspects of the project are progressing as well. Including opening up the junk head in the bowl area As I explore slowing the air and biasing the flow for windowing as well as maintaining/increasing swirl.

XS650 specific (actually engine specific) port design concepts along with some more general port design will be forthcoming for those having trouble sleeping at night.... Porting 102.

Also a video spec'ing the Shell #1 cam as we are getting into the engine/build specific sections.
I believe in actually taking measurements instead of simply accepting the printed specifications whenever possible. I will be using published dyno information for specific torque and power curves.
Have the calibration procedures dialed in.
Extremely confident that the accuracy is above 99%.
Closer to 99.5%. The calibrated plate I ordered has been delayed.
Bruce at PTS was down and out with a virus last week. No not THAT virus...
I am happy to say he is recovered and doing well, but he is a week behind.
So that means the calibration plate is a week away.
I will present the new calibration viseo once it is in hand so the results can be confirmed.
In the meantime we keep on keeping on.

Attached is the Porting 102 video.
Some more thoughts and ideas as well as covering some engine specific math concerning port design.
Hopefully I don't get you lost along the way. Feel free to ask if I do.

Will be spec'ing 2 cams tomorrow. Garrett's as well as mine.
Both are rephased Shell #1.
Will attempt to spec my stock cam tomorrow as well since it's set up.

Edit Note:
In the video, the number I used for the port CSA (cross sectional area) was not from the stock port. It was from the 77% valve formula.
That calculation was
1.57 sq in. which resulted in the 3.16 port saturation lift value discussed.

From the port mapping I shared in an earlier post, the stock port CSA was measured at 34.62mm or 1.36"
Since the stock port is round at that point the area is equal to
1.45 sq in. resulting in port saturation at .292lift.

It is worth noting that the CSA derived from using the Flow Diameter formula based on valve size was
1.47 sq in for a street engine.
That resulted in a port saturation calculation of a nearly identical .296 lift. Formula is dead on for the stock street bike.

Equally as interesting, the D Port had a port CSA (adapted calculation due to complex shape) of approximately
1.31 sq in.
Not surprising with reduced area and higher velocity. That results in port saturation at 2.63 lift.
More velocity, less area resulting in port saturation at a lower lift.

Lastly the engine volumetric formula resulted in a calculation of about
1.2 sq in for optimum port CSA.
The port saturation area for such a port would be 2.41lift.

The trend for performance is a tighter CSA with a port saturation somewhere just under .3 lift.

Last edited: