I almost always use the outer base and torque the injectors, some are 72 inch lbs others are 115 inch lbs. This is a short mostly true description but there are a number of different descriptions depending on which injectors are used. Inner base uses a dial indicator to set the injectors and outer base uses a torque wrench. 027 are used when using outer base circle to set injectors. 023 are used when using inner base circle to set the injectors.