Abstract: A molding machine for a concrete mix includes a frame with a vibratible mold having a vertical through cavity with hollow cores extending downwardly in the mold cavity. A pallet receiver with a pallet thereon is movable upwardly to close the bottom of the cavity. Core tops have openings therein and ventilation pins are receivable to block air passage through the core top openings when the pallet is in mold closing position. Cups with bottom openings are in the cores below the top openings to receive and guide the pins and passageways around the pins permit suction-braking air to move past the pins to the cup bottom openings when the pins move downwardly away from the core top openings.