This photo illustrates the three angles on the intake and exhaust valve seats. A very minor amount of grinding just beneath the throat cut would help the flow. The stock throat diameter on this Mopar exhaust port measures almost 85 percent of the valve diameter (1.270 versus 1.500). The rule of thumb is the throat diameter should not exceed 88 percent for the exhaust, which in this case means there is very little room for modification. On the intake side, the recommended percentage is a maximum of 90 percent. This Mopar intake measured 1.48 inches, which calcs out to 83 percent on a 1.78-inch valve.