Hey Brian, long post here. But as I promised earlier here are some photos of how the modified ports ended up on one of my heads. This is the head that someone had previously tried to port (incorrectly). I did not try to redo it, but rather I cleaned up what they had (crudely) done and tried to make the best of what was left. I'll add comments with the pics to explain what went on. These pics are actually of a exhaust port, but it is identical to the intakes (more on that later). And they after I've reworked it, but maybe it could still use a little more polishing (although I'm not a big believer in the benefits of polishing ports for a street car).
First I should clarify the use of the term "roof" as I referenced it before...we may be thinking differently. I'm referring to the portion of the port that is on the 'short radius' side of the bend between the runner and the valve opening. It is the wall opposite of the valve guide. I believe the theory here is to allow more space around (opposite) the boss for the valve guide (to help accommodate the intrusion made by that boss and the guide), in contrast to the removal of the boss and end of the guide. I suppose technically this might be the 'floor' when the head is sitting in its normal orientation? Looking from the manifold end of the runner this is where the prior owner had made some major changes - removing material to open up the neck and round out the radius of the bend (red arrow):
In the above pic you can see that I also attempted to smooth out the area surrounding the valve guide (better radius the boss around the guide), but I did not eliminate any of the boss's support to the guide nor shorten the guide itself. I'm of the impression for a street engine it is better to keep the guide rather stock.
Here is the same thing looking from the chamber (other) end. Again the red arrow is what I referred to as the 'roof', and where the changes had been made by the prior person. As I understand, part of this approach is to reduce the sharpness of the bend or corner. Think of a hard 90 degree square corner vs one with the corner's "edge" cut off to make more of a radiused bend:
If you compare that to a stock head there is quite a bit of material removed across the "roof". Measuring from the guide to the modified roof, it is longer (taller) here.
Looking once again from the runner end, here you can see what's left of the rather deep casting lines in the runner (red arrows). I removed as much of them as possible without destroying the runner. It is difficult to get the deeper/distal aspects of them due to the curvature of the runner and the guide boss being in the way. I also tried to remove as much of the bad porous holes in the cast aluminum throughout the entire port. The blue arrow indicates the guide boss that I tried to smooth/radius out (described with the first pic):
Looking into the valve seat and port bowl area (below). The seats were not well aligned with the rest of the port/bowl. I do not know if this was due to poor assembly from the factory or if someone has replaced the seats and did not do a good job. But there was a lot of overlap and gaps as the round seat openings (ID) were not centered within the port opening (area around where the red arrow is, below). I removed material from the walls of the bowl in some areas and from the inside circumference of the seats in other areas to try and 'match' the bores (sort of like port matching a manifold). I also tried to straighten out the bowl's walls as it aims toward the valve/seat opening. This is what SteveC describes in his porting guide, allowing a straighter shot for better flow around the valve head and into the cylinder. The bowl walls on the three sides opposite the port (directly behind where the red arrow is, plus the two adjacent walls) are where you can do the most toward that goal. But it gets very tight as you get down by the guide boss (sort of where the tail end of the arrow is sitting here):
Finally a shot of the runner, looking from the manifold end. I tried to make it as round as possible and eliminate the casting flaws. But I did not try to open up the overall diameter or make them significantly larger. Again, for a street application I do not believe that bigger is better, but rather maintain better velocity of the gasses. I did port match them with the manifolds. They were very far off (both intake and exhaust) and required material removal from both the head side and manifolds side. My approach to port matching is to retain the diameter across this transition and not make a "bubble" by opening them up to match the gasket (I described this earlier):
As a result of the port matching, the manifold gaskets will need to be trimmed a little (some aspects of the opening ID). This is because of how far off the stock ports were from one another.
Considering the head had previously been modified and that I had to make further mods to try and repair that damage, I was concerned that the individual ports/bowls were no longer equal to one another (each one relative to the others)...in terms of overall volume. So I used the CC'ing set-up that I made to measure the combustion chambers and measured the volumes of each port (in the head, from where the manifolds mount to the valve seats - with the valves installed). They all came out to within one CC of the others, which is about the margin of error with my apparatus. Although I used some lab grade equipment I had left from my old practice and I have experience in using such equipment, it is highly susceptible to error and each measurement will yield a slightly different value. So I am fine with getting an average of 1cc difference between all readings. According to what I've read that is well within the margin of acceptable tolerance.
I do not know how good or bad this porting job ended up being. I do not have a flow bench. I thought about making one but decided it really did not matter, as I don't intend to experiment with a bunch of heads to refine the technique. Whatever I ended up with is what I have to use on this engine, so it really does not matter how good it is (or isn't). I wasn't prepared to buy yet another head (this one was purchased with the understanding it was a good stock head) and start over, so I just tried to make the most of what I had. This will go on the turbo engine and it is my understanding that porting isn't very critical with a boosted application (compared to a NA one).
On a related subject. I had a great discussion about valve design with the head engineer from Manley Valves while at SEMA. According to him, on these engines the exhaust valve is already extremely large relative to the intake valve size. Seems the original design was not concerned with building any torque, otherwise relying on high RPM's to make more top end HP. The intake valve can be increased in size, but not nearly enough due to the limited room. He said he actually reduces the exhaust valve size in these cases to make the engine more drivable in street applications (i.e. more torque). I suppose that indicates it is more important to get the intake porting right than the exhaust side. However in my case I had already done the exact same porting work on all eight ports (the prior owner made the same mods to all of the ports). And as for modifying the valves to increase flow (e.g. reducing the neck diameter or flattening the backside of the valve heads), he did not recommend it for the same reason. He began offering a lot of technical data to support his view, but frankly the show is so huge that I didn't have time to sit and chat an hour with any one person - so I cut it short and moved on. But I thought I'd throw out the info for others to argue with.