The factory specification calls for a 45 degree valve angle, and a 46 degree seat, what's known as an "interference angle" where there's a single line point of contact at the upper edge of the valve face. It's basically a quick assembly trick at the factory because they don't have to be concerned with exact seat width.
If you choose to use a 45 degree seat on both valve and seat, you'll also need to use a 30 degree upper angle on the seat, and a 60 degree lower angle. That determines the exact width and position of the seating face. The 3-angle method is a much better choice, but it's time-consuming, and you have to have 3 different seating stones for each valve size.
Intake seats need to be .060" wide, and exhausts need to be .090", if you choose to do an exact match on valve and seat angles. Unless you're racing, the interference angle is adequate for most applications.
Jerry
