[Dave Goob Cook]

Jerry, that angle referenced would be the actual valve to deck angle,
I.E.> 23 degree SBC valves must stay within + or - 1 degree, so no relocating the guides or angle milling to roll the valve angle.

The wording would indicate that you cannot alter the area beyond the valve seats, which can now be replaced.

????

The spec used to require that that original valve / seat angles and restricted how many angles you could put on the valves / seats, and the width of the margins and the seat angles.