Wannabriden's D Port Re-Port


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Brandon Ms
I would like to start by saying this endeaver was inspired by @Jack amazing D port thread here. I would also like to thank Jack for sharing his knowledge with the community. I know that I'm not alone in that regard. @Signal made a thread a while back showcasing the flowbench he built as a result of that inspiration here.
No doubt there have been others.

Wannabridin (Garrett) bought an engine built by Hugh (Hugh's Handbuilt) which he introduced in his $Free.99 Project here. The engine contained a D port head which was thought to have been ported by Jack. Jack made mention of what actually happened in this posting

Hugh Head.jpg

Garrett discovered some delamination issues with the epoxy and posted about it here.

D Port Delam.jpg

Short story is I reached out and discussed my intention to build a flow bench at the first of the year to work on D porting my 2 heads. He was in no rush and eventually sent me the head to test and rework. Life has caused a bit of delay from my original timeline but things are finally coming together.

I am a firm believer in having a plan of action, so here is an outline.
The bench should be completed in the next day or two.
After completion of the testing and calibration of the flowbench (calibrated within itself for consistent repeatable readings) I will test the head as received for base information. I will also be running parallel testing on one of my stock heads for comparison. I will be pulling molds of the ports before and after.
The ports as well as the chambers will be cc'd before and after as well; verifying they are equalized.

With no knowledge of the epoxy used or it's application I am thinking it will all need to be removed and then rebuilt following Jack's template while taking into consideration the testing results on the flowbench. To facilitate this I will be remolding the port (once it has been reopened) with clay molding and making changes until it has been been optimized. Then the port will be measured and mapped; clay removed; port cleaned and welded/epoxied; retested. Once completed the head will be heat cycled. The intake manifolds also need to have the ramps built into them and gaskets made.
Good bit of work x 3. (Garrett's Head plus my 2).
Fortunately when doing something you enjoy it isn't really work a all.

The updates on this thread should be much more regular and contain some content that I am hoping may be interesting to others, especially the postings regarding the stock head and it's modifications which may well have a much broader interest. There are a few more tidbits as well which will be touched on as the project progresses. I have been anxious to get to this point and I know Garrett has been also. Let the fun begin.
Yes, I'd love to see flow tests on a basically stock head that's just had the ports cleaned up. Basically, that's all I do, remove the casting flaws and machine marks around the valve seats, and just smooth everything out. I don't enlarge the ports because they're supposed to be borderline too big already. On the several I've done, the bikes seem to run well, possibly having a bit more power and performance, but it's no "night and day" difference. It would be nice to get some verification that this is actually helping.
Yes, I'd love to see flow tests on a basically stock head that's just had the ports cleaned up. Basically, that's all I do, remove the casting flaws and machine marks around the valve seats, and just smooth everything out. I don't enlarge the ports because they're supposed to be borderline too big already. On the several I've done, the bikes seem to run well, possibly having a bit more power and performance, but it's no "night and day" difference. It would be nice to get some verification that this is actually helping.
If the ports are borderline to big for a 650 they are probably just right for 750 BBK.😎
@5twins it is my plan to test the stock head as is (rough casting) with cleaned valves and test small changes from there. A simple cleanup such as you describe which is something I think should be achievable by many within the community. Discovering the data is something I find very interesting. The tests will be shown and not just reported. Everyone can see the results.
At least that is the plan. Also intend to test the difference in valves, from polished to a 3 angle with backcut. Members will be able to see how the changes affect the air flow and make their own determination of worthiness.
Garrett's valves have been lapped, reinstalled and the chambers held the seal without loss for over 24 hrs. I will be cc'ing the chambers as well as the ports for initial starting point data tomorrow on Garrett's head. The stock head is having molds pulled and the material needs to dry. The valves for that head are cleaned and ready to be lapped and installed once the molds have been pulled. Then they will be cc'd as well.
A few ex pics.


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I'm sure that there are some that are wondering about my experience doing something like this.
I've been a gear head for all my life. Like many community members I had a Dad that inspired and encouraged. I was very blessed to grow in that environment. They say birds of a feather....flock together.
That was true in my experience as all my closest friends as well as my younger brother enjoyed building and modifying most anything mechanical, especially ENGINES.
I ran mostly SBF fords, usually in one of my several Mustangs. In those days I DEVOURED every car magazine that I could find. It is no secret to anyone that has ever been serious about making power that the head was the linchpin. I had come across a paper written by Jack Roush containing all the information and specifications for placing a 351 Cleveland head on a 289/302 small block. The Cleveland heads were canted, were lager and provided a better straight shot. Of course I did the mod. But my friends and I also played with the stock heads and seemed to get great results. Response is something you most definitely can feel. We did not do any D porting. Something I had not heard of at that time. What we did do after studying what were professed to be (by the national magazines of course) the best flowing heads was change the rectangular ports into a slight oval shape by welding up the corners.. (THEREBY REDUCING PORT VOLUME) cleaning up the castings, port matching of course. We had no flowbench to test our results. We relied on the OG tried and true methods similar to those mentioned by @Jack. Biggest shop vac we could find, flow balls, and of course the STRING.
Since those early days I have mostly just port matched the engines I work on. I have spent time studying fluid dynamics and new techniques since before I even bought the xs650s with an eye toward this. So it should be clear that I am just like a whole lot of people on this site.
NOT A PRO. Which is the reason I felt building my own flowbench was an absolute requirement.
Especially since I have zero experience on an xs650 head. I am absolutely AMAZED that Jack can do that quality of work without one. But as he says (and I very much relate to my experiences detailed above) that once you have done enough, your experience can guide you to those results.
I've grown a bit OCD as I have aged and my desire to be able to measure any improvements is important to me. It is my hope that this hopefully straightforward information and data can be beneficial for others that are curious about the reward/benefits of some of these modifications.
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Garrett's head molds...
I've molded before but not using this technique.
Trying to find a way of pulling these cheaper.
They turned out pretty good but each has some issues. I believe I have identified the causes of the problem areas. They still need cleaned and some minor repairs but overall I am pleased with this initial effort. I will have this process dialed in soon. I will follow up with more detailed mold pics once I have completed addressing the issues. I am expecting this next set to be a bit better. There is a good bit of detail to be gleaned.


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The thing that makes this all possible for me is the flowbench. Did a LOT of studying on this over a long period of time before I actually built this.
I decided on a system quite similar to @Signal flowbench although my decision on that design was made before seeing his. I guess we just had similar thoughts. I did reach out to Signal privately to pick his brain a bit and am very greatful for him taking some time to assist.
Basically I have a "vacuum box" connected to a "settling chamber" via a 6" pipe.
A 3" pipe connects the "settling chamber" up through my workbench to the head fixture.
The vacuum chamber houses 7ea high CFM vacuum motors to provide the 28" water depression which is a porting standard.
The shop vac and string gives solid information but the air tells you more at a higher vacuum; often giving discoveries that would otherwise not be seen. There is a U-shaped manometer which measures the actual depression. It should always be reading whatever depression you are testing at (usually 28" water). There is also an inclined manometer which is used to measure the actual flow through the test piece. There are calibration plates used to test the bench as well as set the inclined manometer I'll explain this more as we go forward. There is also a fixture required that allows one to open and close a valve to reach whatever lift value is being tested at the moment. The dial indicator will be attached to this fixture as well in order to accurately measure those lifts. Finally a way is needed to measure the air flow.
There are several possibilities. The simplest 2 in my opinion would be a differential preassure meter. Accuracy requires a temp and humidity.
I chose a CFM meter which takes temp and humidity and converts it all. Makes it very easy to use. It also connects with my laptop giving me a chart and data for every half second. I will have to dial it in to maximize accuracy. I am looking for CONSISTENT, REPEATABLE measurements.
Some of the tests may result in small changes and we want to see them. The readings will be checked with some math for the time being.
I intend to add a second cfm meter and eventually a differential pressure meter across an orifice plate set within my 6" pipe (similar to what you can see looking at Signal's set up. These are only to help in setting and keeping the flowbench calibrated. Including a few pics. Some were taken in progress and may be more of a "mock up" type of pic. Also keep in mind that the flowbench is not yet complete. Wife has an outpatient procedure tomorrow so at least Thursday if all goes well. Also a pic of the flow balls...


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I would very much like to see just how far one can go into these heads based on measurements from my locating tool. I understand that occasionally there are xs650 orphaned heads (missing the matching rocker box). If anyone has one of these that they would like to donate to the cause please let me know. I will provide DETAILED data to the forum based on my findings. I will happily pay shipping.
Please PM me.
Excellent write up. Thanks for sharing this experience and information here.

We relied on the OG tried and true methods similar to those mentioned by @Jack. Biggest shop vac we could find, flow balls, and of course the STRING.
Can you post a link to this information or explain it a little?

Also what is meant by 28" water? Is that a constant on the manomeeter, if so where do you read the vacuum changes? What moves if it's at 28" water.
I'm guessing the 28" water means the water pressure at that level? Like every certain # of feet down is another 14+pds, another atmosphere of presure?
All of this information is forthcoming along with video showing everything. But the basic answer is this. The testing pressure manometer is u shaped and I am using water as the medium.
Common practice although there are a few various options available, some specifically for this. We all know water levels, so the water level of each side of the tube will be at the same height at atmospheric pressure. See the pics below. One end of the tube remains open to the atmosphere and the other is placed within the setting chamber (or possibly at another point downstream within the vacuum pull (path).
The higher atmospheric pressure will push the water down the tube toward the low pressure causing the water to rise on the lower pressure vacuum side. The difference between the two is measured in inches. The measurement is the DIFFERENCE and not just the side that rises.
When one goes down an inch, the other goes up an inch. That would be 2" of water.
That manometer guage is to measure the pressure you have chosen to test at. 28" is simply a standard. There are some that test even higher and many that test at less. The 28" is pulled across a calibration plate which allows a known quantity of air to pass at that given pressure.
For ex: (using easy non accurate numbers)
If I am using a calibration plate with a 1" hole.
Placing the plate on the bench to set the 28" of water. Adjust the vacuum motors until the steady 28" has been reached. Just say the 1" plate will flow 100 CFM @28". Every time I place that plate on the bench and pull a steady 28" I should be reading 100 CFM. Hold that thought.
Reread if needed.

Now as for reading the vacuum changes on the piece being tested...
The vacuum changes are measured from an inclined manometer which is used somewhat differently and it is calibrated to the test pressure in conjunction with calbration plates to read 100% flow at the chosen calibration plates CFM rating. The incline manometer is adjustable and it's scale is not in inches. It is in percentage which is NOT LINEAR. Adjust the Inclined manometer to read 100% with the calibration plate and the u shaped manometer @28".
So using the examples numbers of 100CFM using a 1" plate; obviously 100% would be 100CFM... 90% would be 90CFM.. etc.
That is step one calibration.

Note: The calibration plate should be able to move more air than the test piece can flow.
It should be as closely matched as possible to the CFM while remaing slightly higher.
The closer the match the more accuracy.

To test the actual head, the calibration plate is removed and the test piece set up.
Run the testing pressure on the U shaped manometer to 28" and take the percentage reading from the inclined manometer.
Say we are testing at .4 lift.
Say the incline reads 78%.
That would be 78% of the previously calibrated 100CFM. 100CFM X .78 (percentage)= 78CFM
I have a CFM meter inline and it should agree with the incline. That is a double check.

I hope the long explanation was not TOO confusing and yes it can seem a bit convoluted but it is actyally a relatively simple procedure.
Again there will be videos upcoming that will show everyone everything. Hopefully they will answer most questions although I will certainly do my best to answer any that are needed. The calibration phase of the flowbench should start this weekend.
(My wife just had some outpatient surgery this morning and I will be taking care of her for a couple of days)


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