...This is an Example of polishing the Sharp Edge and Turning Radius of the Valve Bowl. I couldn't find a FORD Head this a Chevy. But, the Principle is the Same. Bowl Polishing is always done Before the 'Valve Job', if the Seat should be Marred by the Burr, it may be fixed during the 2 angle job. See in the Before and after pictures, the 60 Degree Angle, and Sharp Edge are Removed and inner Radiused. Intake and Exhaust both done is good for a Increase of 20-40 Horsepower. That helps a 351 Cleveland approach 500 HP with 4V Iron Heads. When Ran with Dual Quads and Higher Compression.
MJ