cylinder head inasmuch as the spark plugs of the engine are normally mounted in the cylinder head it is to be understood however that the invention can also be practiced in conjunction with the mounting of spark plugs for engines in other components of the engine than the cylinder head the cylinder head assembly 11 is comprised of a cylinder head 12 that defines a recessed area 13 that cooperates with the cylinder block cylinder bore and piston all of which are not shown in a known manner an intake port 14 opens through one side of the cylinder head and enters into the combustion chamber recess 13 a poppet type intake valve 15 is slidably supported within the cylinder head 12 in a known manner so as to control the flow through the intake port 14 in a similar manner an exhaust port 16 opens through the opposite side of the cylinder head 12 and communicates with the combustion chamber 13 a poppet type exhaust valve 17 controls the flow through the exhaust port the intake and exhaust valves 15 and 17 are operated by means of a single overhead camshaft 18 which is driven from the engine output shaft in a known manner the camshaft 18 has lobes 19 that cooperate with rocker arms 21 that are journaled upon rocker arm shafts 22 for operating the valves 15 and 17 in a known manner this valve operating mechanism including the camshaft 18 is enclosed within a cam cover 23 a spark plug 24 is mounted in the cylinder head 12 and has its spark terminals 25 disposed within the combustion recess 13 for firing the charge therein in a known manner the spark plug 24 is mounted so that its longitudinally extending axis indicated.