Abstract: A light alloy piston having an annular cooling passage in its head portion is prepared by a process wherein a permanent mold, preferably having a steel shell and a water cooled bottom, is filled with the molten piston alloy. Thereafter, core elements, particularly a salt core for forming the cooling passage are introduced into the molten material by means of a holder and the permanent mold is held at an elevated temperature by external heating. The permanent mold is then lowered into a water bath for a given period of time. The soluble core, which has a specific gravity lower than that of the molten light alloy, is forced into the molten material to the desired position and depth using a holding device. The holding device is withdrawn from the remaining molten material when the solidification of the molten material has proceeded to the underside of the core.