Patent ID: 8716923

Claim:
A spark plug assembly, comprising: a spark plug comprising an inner conductor, an outer conductor, wherein at a lower end of the plug, the inner conductor and outer conductor respectively terminate to define a gap there between across which a spark is created in use of the plug, an insulator disposed between the inner conductor and outer conductor, and a first indexing mark on an upper portion of the plug; and an adapter comprising a sleeve that defines an inner bore that receives the plug through an upper end of the sleeve and a thread on an outer surface of a lower end of the sleeve opposite the upper end, a retainer connected between the sleeve and the plug so that, when the plug is inserted into the bore so that the inner and outer conductors extend out of the lower end of the sleeve and the gap is outside the sleeve, the retainer retains the plug in the bore against movement out of the bore through the upper end in a direction along an axis of the bore and the retainer allows rotation of the plug about the axis when the plug is inserted into the bore and retained by the retainer, and a plurality of second indexing marks disposed on the adapter so that, upon insertion of the plug into the adapter, alignment of the first indexing mark with any one of the second indexing marks brings an opening of the gap to a predetermined rotational position with respect to the axis.