Grooved cylinder base stud is specific for use with the hollow cylinder barrel dowel. (2) are used with the remaining (6) plain studs.
Cylinder base stud is 1-5/8″ long with 3/8-26 TPI threads and is grooved to identify it as the stud used in the position on the cylinder base where the hollow dowels are installed.
Cylinder base studs are used to attach the cylinder barrel to the crankcase.
Cylinder base studs are installed using a special stud installer tool or can be installed by tightening (2) nuts together to form a bolt head, so a socket or spanner can be used to tighten the stud.