Abstract: A water-jacket core and slab core for a V-block of an internal combustion engine are assembled into a jacket and slab sub-assembly and are placed on an apparatus for the automatic insertion of staples in the jacket and slab sub-assembly to thereby retain the water-jacket core and slab core together in the jacket and slab sub-assembly. The apparatus automatically positions four automatically operable staple guns so that each of the staples is inserted with one tine of each staple in the water-jacket core and the other tine of each staple in the slab core with the crown of each inserted staple lying across the interface between the assembled water-jacket core and slab core and retaining the water-jacket core and slab core together. As few as two staples per sub-assembly can be used to retain the water-jacket and slab core in their sub-assembly.