Patent ID: 7305763

Claim:
A method for making an improved cylinder head having a predetermined port configuration with selected double walled ports for an internal combustion engine, comprising the steps of: providing a cast cylinder head for an internal combustion engine with selected ports for port liners, said selected ports having a larger diameter than a standard port size for the cylinder head by a preset amount as determined for a double walled port configuration; providing protrusions in the walls of the selected ports for facilitating formation of an air gap; positioning insert sleeves in the selected ports of the cylinder head; and applying hydrostatic pressure to the insert sleeves within the selected ports of the cylinder head to hydraulically expand the insert sleeves up to upper surfaces of the protrusions in the walls of the selected ports for making hydroformed port liners within the selected ports and for forming said air gap between an outer surface of each hydroformed port liner and the wall of the selected port.