An injection-compression plant for manufacturing PET performs comprises an extruder (1) to produce a melted resin, a distribution joint (3) for distributing the melted resin from the extruder (1) towards the injection-compression molds (9′, 9″, 9″), gathered in modular groups of three on supporting frames (21) arranged about the peripheral surface of the rotary carousel (2). The joint (3) allows to transfer the fluid thermoplastic resin from the stationary channel (10) of the extruder (1) to the lateral feeding conduit (27) of each molding module (9), said lateral feeding conduit being rotating with the carousel (2). The injection-compression molds (9′, 9″, 9″) have the two half-molds forming the molding cavity (41′, 41″, 41′″) connected by means of bayonet couplings to the frame (21). The molded preforms are extracted from the carousel (2) by means of a wheel (50), which transfers them to an air cooling device (51).