An opposed-piston engine assembly is disclosed including a first cylinder liner containing a pair of first pistons that move toward one another in one mode of operation and away from one another in another mode of operation. The pistons are coupled to first and second crankshafts. Multiple block segments arranged in a side-by-side abutting relationship form the engine block including a first outboard segment, a first inboard segment, a second inboard segment, and a second outboard segment. Tensile members extend through the block segments tying them together as one structural unit. The first and second inboard segments abut one another at a seam and include bores that cooperate to receive the first cylinder liner. The first cylinder liner includes a liner support collar that is received in counter-bores defined by the first and second inboard segments at the seam between the first and second inboard segments.