An apparatus is disclosed including a first end defining an inner passage along a first inner surface of the first end, where the inner passage has threads structured to receive a spark plug. The apparatus further includes a second end opposite the first end and extending into a combustion chamber of a cylinder, the second end defining a pre-combustion chamber along a second inner surface and threads on an outer surface structured to thread into a spark plug hole in a cylinder head, which may be an enlarged spark plug hole. The second end includes holes that fluidly couple the pre-combustion chamber of the second end with the combustion chamber of the cylinder.