This shelf that extends all the way around the intake bowl is excess metal left over after factory machining procedures. That is a heck of a ridge. I will grind that down and smooth it to assist in good flow. The intake bowls tend to have more of this shelf than do the exhaust bowls; but all the bowls will benefit from some grinding and blending.

The objective is to grind, shape and blend the metal around the bowls, transitions, and runners in order to make them all as uniform as possible; and without removing any more metal than necessary to achieve that goal.