Emission requirements are driving a change from the current 7.5 mm injector tip to a 6 mm tip on most GM SIDI gasoline fuel systems. This change is due to both higher fuel pressures and packaging constraints, and affects SGE, LGE, and future V8 engines.
Injector seals are installed using GM-51955, which includes two protectors due to the placement of the two injector seals, a seal pusher to ensure the seals are not over-stretched on installation, an initial seal compressor due to the hardness of the seals, and a seal sizer to put the seal at the final 6.5mm size for installation into the head. Installing the seals without using GM-51955 will damage the seals and could result in fuel or combustion pressure leaks.