Changing Intake ports to a D shape for better flow.

Frontal shot of guide, take notice of the bulgy guide boss and the restriction around the sides and towards the roof.
xs guide install 2.jpg
 
Here is how it looks after a diet reduction. I really struggled trying to take a better visual image but I have a couple for you to examine how I shifted the inner portion of the roof over towards the middle of the guide in order to turn flow and how I angled the the roof up on the outer sides of the guides. How I modified these areas is crucial in yielding big flow gains. I have approximately 4.5 hours just working the guide areas,there's alot of finger sanding just to get the right profile I'm looking for,I'll explain later how I achieve it.
XS EP right 2.jpg
 
Finished this one port this morning, one more to go. you can visually see the guide boss work much better in this image. I dropped the outer floor some to to expose more of the valve head and what have I found is this slight mod helps stabilizes the flow in the 350 - 400 lift range to around 140 to 145 CFM as the E/P can flow up to 80% plus intake flow at certain lifts.

xs ep finished.jpg
 
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Hey Jack, wie geht's deinen Fingern;) I've a question in regards to the floor corner. How far in the direction of the valve did you work there? Goes area where to remove material behind the bend towards the valve?
 
In the photo of post 90 there is a visible area where you take away some minor casting. I think you just eroded protruding material, don't you? At this spot in OEM casting there are 1 or 2 little but clearly feelable "hills" I have noticed at different heads. With my current head, there were ledges that I leveled out to the surrounding material.
The goal is to create a transition to the valve area that is as smooth as possible if I have understood it correctly. Am I right there?

In the heads I have, you can often feel a sharp edge in the transition from the combustion camber steel to the port. This edge differs from head to head and port to port. I remember that one head even has a sharp edge on one port and smooth on the other. It is as if the cast rarely fits to the steel from combustion camber exactly there. Do you also work on this area?

Did E/P means Exhaust Port?

i hope you understand me? it's hard to write in english, especially on a subject i never had in school english;)

Tausend Dank!
 
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Yes E/P = exhaust port
Yamahas casting of the XS head will vary from head to head, port to port,a lot cast shifting and how they machined the 60 degree bottom seat cut will also
vary right down into the bowl area. Basically you pick the best head with least amount of core shift or deal with what you have on hand.
All the flaw casting on this head has been remove and blended in,your good to go on the E/Ps at this stage and I'll touch them up with some
400 grit when the D intakes are done. Here are the completed E/Ps
 

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It is too late now, but perhaps it would be a good idea to color the entire port surface with a dark-ish permanent marker, then grind out a specific area, take a picture or two of just that, then apply permanent marker again, and work the next area, and so on. This would make it a little bit easier for us dummies to understand what areas are most important to focus on.
 
I will be posting exhaust port dimensions along with what areas work to and what to look for regarding short turn and outer port walls. I can't stress enough the importance of working the guide ,guide boss and the guide side radius leading to the roof, these are the key elements. Get those right and the engine will have a wider power range and pull like a freight train.
 
I will be posting exhaust port dimensions along with what areas work to and what to look for regarding short turn and outer port walls. I can't stress enough the importance of working the guide ,guide boss and the guide side radius leading to the roof, these are the key elements. Get those right and the engine will have a wider power range and pull like a freight train.

Right up my alley as I like tall gears and engines with lots of bottom end.
 
The dimensions for the EP exit will vary from port to port and what I've found from flow testing, having little to nothing to gauge by has no impact on flow and this includes the floor,except for
for the outer floor of the port where it curves up, you can bias the flow to some degree. My very first XS head that I ported had absolutely no floor to work with and to this date,I've yet to match it's outstanding flow curve and that's the truth,all the gains came from working the bowl, guide,guide boss,roof and turning the inner portion of the bowl next to the guide and alining it with the outer port wall for a straighter shot out the port
Dimensions height and width are 1.369 - 1.369 34.78mm-34.78mm

xs ep 3.jpg
 
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In this image when working the guide boss,you want to taper it. The line on the left from frontal view you want to cut it straight and line on right cut it a taper working towards center of guide.
Theres plenty of meat in the guide bore for support.
Before proceeding working the guide areas, you first work the bowl removing casting flaws and blending the bowl.

EP done 2.jpg
 
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Jack,
I've been reading this thread with great interest and admire your work. What I would like to see is an XS that makes more torque at much lower RPM than most builders shoot for. Perhaps something that would work well with a big bang engine. Do you think your port designs could do that?
With a stroke of 2.913" the engine doesn't produce enough pull or piston sweep volume on the intake port for low end toque until higher up the RPM
range where power is produced in the XS. For street use you build,em like a small block chevy 302 ,ford 302 and Mopar 340, for building lower end
torque. Longer spigot manifolds, Shell #1 cam, small diameter headers,big bore kit, 32-34 flatslide carbs and my opinion a head with small port volumes
to enhance port velocity without sacrificing CFMs. It's takes a combination of all of these for a balanced all around package but for me, you start with the head,that's the key,it's the soul of any engine.

As far as my ports go,it's just another option with smaller port volumes, increased velocity,no reduction in CFM, the flow curve comes in super hard from 200 to 300 by 60 plus CFMs and tapers to 20CFM gain at 400 lift but well see how this head flows when I'm done. It does take alot of surgery to restructure these ports the way I do it .
 
To give you an example of what's involved here, it took me about 7 hours just to do this one port along with reworking the bowl, stopping taking
measurements,etc and still haven't raised the floor yet. Notice all those aluminum shavings on the table:yikes:
Chris's head.jpg
 
You know I started this porting project back in 2000 something and always had to place it on the back burner do to family,supporting the kids and their family and now that I'm getting at the age where you never what'll happen health wise,it was time to share this knowledge thinking outside the box that not one head fits all. It just happened that Chris came along who expressed great interest and thought why the hell not and I gave him one heck of a deal
just for testimonial feed back. All the previous flow testing on this port was done on a shrouded valve bathtub combustion chamber and after a few
changes in the roof and short turn, the flow #s shot up and now I've been given an opportunity thanks to Chris to see what this port is really capable of flowing with non shrouded valves.

If this head pans out to exceed or if flow remains consistent of past testing then yes I'll consider taking on a few projects. Money wise,haven't given it
much thought cuz I know it works and I enjoy porting this head for once.
 
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