The disclosure relates to a system and method for sizing of system components in a dual fuel port injection system. The system includes a pressure regulator and a safety shut-off valve that feeds a main gas rail. The gas rail is operatively connected to a gas admission valve by a gas jumper tube. The gas admission valve is operatively connected to a gas admission port in a cylinder head or to an intake runner via a gas delivery tube. The gas admission valve has an effective cross sectional area that is defined by the actual cross sectional area multiplied by a modifying coefficient. The components of the system are sized based upon the effective cross sectional area of the gas admission valve.