Abstract: A spark plug having an internal resistor and resistor-bore seal is disclosed. The spark plug comprises a shell, an insulator assembly carried by the shell and a ground electrode structurally integral with the shell. The insulator assembly comprises an insulator having a firing end and a terminal end, and a bore extending therethrough, and a center electrode within the bore of the insulator, and having a firing end firing in spark gap relationship with the ground electrode. The assembly also comprises a resistor positioned within the bore of the insulator and in electrical contact with the center electrode. The longitudinal position of the resistor in the bore of the insulator is radially inward of the shell. The assembly also includes an electrically nonconductive and substantially gas-impervious seal compacted between the walls of the bore of the insulator and longitudinally extending walls of the resistor. The electrically non-conductive material can be covered by an electrically conductive cup.