Insulating sleeve having an insulating-gap for a cast cylinder head

An insulating sleeve for a port line of a cylinder head, comprising:

• an outer-sleeve having an interior surface defining a periphery inlet flange surface and a periphery outlet flange surface;
• an inner-sleeve having an exterior surface defines a periphery inlet flange surface and a periphery outlet flange surface;
• wherein in the inner-sleeve is disposed within the outer-sleeve such that a portion of the exterior surface of the inner-sleeve is spaced from a portion of the interior surface of the outer-sleeve defining an insulating gap therebetween,
• wherein the periphery inlet flange surface of the inner-sleeve is joined to the periphery inlet flange surface of the outer-sleeve, and
• wherein the periphery outlet flange surface of the inner-sleeve is joined to the periphery outlet flange surface of the outer-sleeve.

A method of making a cast cylinder head having a cast-in insulating sleeve, comprising the steps of:

• providing a cylinder head mold having a form core defining a port;
• assembling an insulating sleeve onto the form core defining the port;
• and
• filling the cylinder head mold with a molten metal;
• wherein the step of assembling the insulating sleeve includes disposing an outer-sleeve over an inner-sleeve defining an insulating gap therebetween.