Spark plug assembly for an internal combustion engine

A spark plug assembly comprising:

• an insulator body extending along a longitudinal axis from a first end to a second end, the second end defining a tip, the insulator body defining a first face extending radially, the first face positioned between the first and second ends;
• a central electrode extending through the insulator body from the first end to the second end;
• a side electrode connected to the insulator body for rotation therewith;
• a retainer connected to the second end of the insulator body, the retainer defining a second face extending radially;
• a jacket rotatably supported by and surrounding the insulator body, the jacket positioned between the first and second faces, the jacket defining an inner surface and a threaded outer surface;
• and
• a bushing rotatably supported by and surrounding the insulator body, the bushing positioned radially between the jacket and the insulator body, the bushing positioned between the first and second faces, the bushing defining a tapered outer surface to mate with the inner surface of the jacket.

A method of assembling an engine, the method comprising:

• providing a cylinder head with an intake valve port and a threaded spark plug port;
• providing a spark plug assembly with an insulator body extending between a terminal and a retainer, the insulator body defining a first face extending radially, the retainer defining a second face extending radially,
• positioning the spark plug assembly into the threaded spark plug port;
• indexing a side electrode to a selected radial position relative to the intake valve port by rotating the terminal, wherein the terminal, the insulator body, and the side electrode are connected to one another for rotation therewith;
• and
• screwing a jacket of the spark plug assembly into the threaded spark plug port while maintaining the side electrode in the selected radial position such that a threaded outer surface of the jacket mates with the threaded spark plug port, wherein the jacket is supported for rotation on the insulator body between the first and second faces, with the first and second faces limiting translational movement of the jacket;
• wherein screwing the jacket into the threaded spark plug port causes an inner surface of the jacket to engage and deform an outer tapered surface of a bushing positioned radially between the jacket and the insulator body, thereby securing the jacket to the insulator body.