An opposed-piston engine assembly comprising: an engine block; a first cylinder liner disposed within said engine block that defines a first cylinder for receiving a first piston and a first opposing piston; said first cylinder having a first longitudinal axis that extends coaxially through said first cylinder; said engine block having multiple block segments (92a, 92b) disposed in a side-by-side abutting relationship including a first inboard segment and a second inboard segment; said first inboard segment defining a first bore and said second inboard segment defining a second bore; said first bore of said first inboard segment being disposed in fluid communication with said second bore of said second inboard segment; and said first and second bores (104a, 112a) being co-axial with said first longitudinal axis and aligned with one another such that said first and second bores (104a, 112a) cooperate to receive said first cylinder liner, wherein said first cylinder liner has a cylinder wall presenting an inner surface that defines said first cylinder within said first cylinder liner and an outer surface that is opposite said inner surface, characterized in that said first cylinder liner includes a liner support collar disposed intermediately along said first cylinder liner that extends annularly about and radially from said outer surface of said first cylinder liner to form a stop, and at least one of said first inboard segment and said second inboard segment including a counter-bore (106a, 114a) that is coaxially aligned with and that extends annularly about one of said first bore and said second bore to receive at least part of said liner support collar of said first cylinder liner. an engine block; a first cylinder liner disposed within said engine block that defines a first cylinder for receiving a first piston and a first opposing piston; said first cylinder having a first longitudinal axis that extends coaxially through said first cylinder; said engine block having multiple block segments (92a, 92b) disposed in a side-by-side abutting relationship including a first inboard segment and a second inboard segment; said first inboard segment defining a first bore and said second inboard segment defining a second bore; said first bore of said first inboard segment being disposed in fluid communication with said second bore of said second inboard segment; and said first and second bores (104a, 112a) being co-axial with said first longitudinal axis and aligned with one another such that said first and second bores (104a, 112a) cooperate to receive said first cylinder liner, wherein said first cylinder liner has a cylinder wall presenting an inner surface that defines said first cylinder within said first cylinder liner and an outer surface that is opposite said inner surface, characterized in that said first cylinder liner includes a liner support collar disposed intermediately along said first cylinder liner that extends annularly about and radially from said outer surface of said first cylinder liner to form a stop, and at least one of said first inboard segment and said second inboard segment including a counter-bore (106a, 114a) that is coaxially aligned with and that extends annularly about one of said first bore and said second bore to receive at least part of said liner support collar of said first cylinder liner.