The D-port was just a idea that came out of me reading this, http://datsun1200.com/modules/myalbum/photo.php?lid=1777 (Scrool down), where D suggests porting it that way.

I was very skeptical to weather, or not, it would break into the water jacket, and it properly will... So the idea is scrapped...
Just for fun, how bad is it to block off the water-passage above the ports?
Thinking about the good-old gigant raise tube insert, for the downdraft/high-angle intake :D (*_*')

My plan is now, (to not go bonkers)... to just enlarge the whole port by 1-2MM and raise the top by 3-5MM, depending on how thick the wall is?
My guess is that it is around 5-10MM (7MM?) when I compare the wall thickness, through the pic. by (ang94541), with the bolt, which I believe is a M10 bolt( ? )

EDIT. I talked with my farther-inlaw, here in Denmark we have a very special guy. He is a old retired man, ex-mechanic/machinist, that back in the day had his way around some motors. He was an absolute GURO! He specialised in Moris's and get this. When everyone else hit top end power, and nobody could squeeze more power out from them, he didn't want it to be it, so he designed a new head(or worked with the original, dont know all the details)... with crossflow... And made 20HP ATW more than anybody else!
I need to get in touch with this guy. If I can get him to talk, or if I got the founds, let him do wonders to my head He loved doing that sort of stuff as I understood(ad a good price), and back in the day there should have been a couple of Datsun's around up here, so he might have had his fingers in one already!

hit the water jackets on the inlets no worries just fill with devcon
http://www.pitroad-ts.com/tuning-page/Ts-cup-2/ts310-engine.htm







the reverse D port could increase the tumble as there is already enough swirl in the
A series chamber design but manifold would be a killer to do.
The original poor short turn radius on A series heads could be there to keep the charge
on the important part of the valve not right across it which could create undesired eddys.

keeping the charge together as tight as possible, as deep into the downward piston
swirling tightly away from the cylinder walls is crucial and short turn radius opened up
sometimes disturbs this desired flow characteristic matched to the chosen stock chamber.

A small cc due to shaving the head for comp can also be upset with increased short turn radius
as it could prefer deeper set valves. Its all very tricky to balance a real art.
As a natter of fact this mod showed no improvement in some race applications so Nissan
engineers know alot more than us tinkerers

So the water jackets on the inlet dont "need" to be there?

If I where to do as they have done there (Assuming that the smaller round holes is to locate and hold the Metal-Putty(that's what devcon is right?), That would benefit the motor heaps, better flow than a GX ( ? )
Should I then also do the valves? The seats I'll prop get re-cut as the motor have been sitting for a long time and 2 are leaky
(or if not I have 2 cyl. with the worst looking rings you could imagine... Compression; 12-6-11-8 on the four *_* )

Additional question, Can you just grind the valve-guide away as you want? That's not bad thing to do?
Just asking, as I see lots of porting jobs where they do it, and other where they just work it to a smooth transition around it.

EDIT: (After I saw your Edit.)
So it don't work to raise the port like that? Hmm, that interesting.
The design I made could work? Using Devcon to block the holes I make with the upside down D, and enlarging the port all around a little?

I have given up a bit on the D-port design... The raising of the port + D makes no room for the mounting screw :/
But have finished my oval port design (Y)

big round ports are the way as in the pic and will make nice inlet manifold all even