For comparison, if you use the correct seat insert, there is very little blending required.

Since the transition from the seat into the bowl has more of the correct shape, and there is less material removal needed to get a smooth transition from the seat into the bowl, you get about 10cfm additional flow, with about 1/2 the effort.

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68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads