Since the stock ports are, if anything, too large to begin with, the actual amount of material that is removed by the Lillie head's CNC porting process is very minimal. No material is added to the ports before the CNC porting process. In fact, on both the intake and exhaust ports there are areas where the cutting tool doesn't alter the shape at all.
Also, we've learned that the head castings vary considerably, so there will be material removed from a given area in one head that is untouched in another.
The intake valve is a approx. 1mm larger and the exhaust is about 2mm. The model for the valve head shaping is the H-D XR750, and a standard racing three angle valve job is the seating spec.
Differences of as little .005" affect flow, and when you combine that with the subtle nature of the changes made, it is very difficult to visualize where the magic lies.
There is also some material removed and blending done around the value pockets. This is crucial, but once again subtle. An exception is around the guides where the modifications are obvious but straightforward.
The emphasis on the exhaust port is more related to reduction of turbulence and less upon more theoretical flow.
Again, looking at the completed head, which doesn't really look that much different than a stocker, the buyer might ask if they got their money's worth? Yet, when the two are compared on a high end, state of the art flow bench the Lillie head flows 56% better on the intake side and 27% more on the exhaust than the stock unit.