Internal combustion engine having a permanent ground electrode and replaceable center electrode element

A method of manufacturing a ground electrode for use with a spark plug center electrode element installed in a cylinder head of an internal combustion engine, said cylinder head having an outer wall, an inner wall forming at least a portion of a combustion chamber, and a bore for receiving the spark plug element between the outer and inner walls along an axis, said bore including an intermediate transverse seat for engaging a shoulder of the center electrode element installed through the outer wall against movement toward the inner wall, said method comprising the steps of:

• (a) forming a ground electrode comprising a peripheral wall, a first, open end and a second, at least partially closed end,
• (b) permanently affixing the ground electrode in the cylinder head bore such that said peripheral wall is partially received in the cylinder head bore through the cylinder head inner wall and the closed end is disposed beyond the cylinder head inner wall for protruding into the combustion chamber, said ground electrode open end being in registration with said bore,
• (c) axially inserting a mandrel in the bore through the cylinder head outer wall, said mandrel having an end for engaging the ground electrode closed end,
• (d) working the ground electrode closed end against the mandrel end to position said end in a preselected axial relation to the seat, and
• (e) removing the mandrel.