Q: What is the proper way to angle mill? Should I change the intake side or the head or change the intake?
Common practice is to do all work to the cylinder head. Then if the manifolds are changed or heads are changed, they don’t have to be done as sets (2 heads and a manifold). Manifolds can be changed at will without modification when all the work is completed on the heads.
Q: What is the formula for this?
Different heads have different requirements. Check out the chart below for more information.