Combination metal and elastomer cylinder head gasket

A gasket for interposition between the interface surfaces of a cylinder block of an internal combustion engine, the cylinder head and block having one or more cylinder bores defining combustion chambers of the engine, and one or more passageways for the flow of fluid through the cylinder head and block, said gasket comprising:

• a metal retainer member having generally planar first and second surfaces with one or more cylinder bore openings and fluid port openings formed therethrough, said fluid port openings comprising a first fluid port opening defined by a first given outer periphery and at least one corresponding second fluid port opening defined by a second given outer periphery substantially the same configuration as said first given outer periphery, each of said cylinder bore openings being configured for registration with a corresponding combustion chamber, and each of said fluid port openings being configured for registration with a corresponding passageway;
• and
• elastomeric members attached to said retainer member about each of said fluid port openings, each of said elastomeric members having a seal portion extending along the given outer periphery of each fluid port opening for sealing the corresponding passageway thereof, and a diaphragm portion extending from said seal portion at least partially into an interior of each fluid port opening for covering at least a portion of the corresponding passageway,
• said elastomeric members including a first elastomeric member attached to said retainer member about said first fluid port opening and a second elastomeric member attached to said retainer member about each second fluid port opening, said diaphragm portion of said first elastomeric member being perforate and defining a first fluid port of a first predetermined diametric extent, and said diaphragm portion of each second elastomeric member being perforate and defining a second fluid port of a second diametric extent smaller than said first diametric extent effective to meter the flow of fluid through said second fluid port relative to the flow of fluid through said first fluid port.