Most Chevrolet ports are designed with a bias towards the center of the cylinder. Airflow has a tendency to want to move in that direction, and generally, the higher flow areas of the intake aperature are located on toward the cylinder's center.
Increasing valve size from 1.94" to 2.02" on the early fuelie type heads is a common practice. Airflow will actually suffer if some sort of deshrouding operation is not performed on these types of heads. A situation where the intake valve is directly against the port wall creates fuel wash and poor swirl and disrupted flow.
Going to larger valves without doing the deshrounding operation can actually hinder flow over the stock valve size.
The amount of deshrouding doesn't have to be a huge amount, bearing in mind that airflow has a tendency to move towards the cylinder's centerline.
Most aftermarket performance heads are adequate in this area. Most factory heads, except for maybe the newer fast burn or Vortec heads are not. The factory Vortec head is a good example of what is necessary for optimum flow numbers.