A crosshead system for a swashplate engine such as a Stirling cycle type. A plurality of crossheads are constrained to move in a reciprocating fashion by travelling along a pair of parallel guide rods. The crosshead system further includes a mechanism for adjusting a clearance between the crosshead elements and the opposed parallel face surfaces of the rotating swashplate. The adjustment mechanism includes a threaded adjuster cup which is maintained in a lock position through a fastener which drives a conical cone into the conical inside surface of the adjuster sleeve thus fixing its rotated and hence linear position.