Low cost insertable type port liner

Claim 1

For use in an internal combustion engine having a housing mass enclosing a combustion zone in one portion thereof, apparatus for modifying the heat transfer characteristic through the walls of an unlined passage extending through said portion of the mass of said engine, said passage walls defining an outer wall and an interior space, insulating means in said passage conforming substantially to the inner contour of said passage outer wall and having a layered assembly with at least five radially distinct zones, the outermost or first zone of said layered assembly consisting of a room-temperature-curable silicone plastic in the thickness range of 0.02-0.05 inches, a second zone consisting of a plain carbon steel sleeve containing less than 0.6% carbon and having a thickness in the range of 0.015-0.018 inches, a third zone consisting of a coating of room-temperature-curable silicone plastic in a thickness of about 0.01 inches and having a melting temperature greater than 200° F., a fourth zone consisting of an insulating wool or fiber mat in the thickness range of 0.020-0.060 inch providing numerous enclosed trapped air spaces, and a fifth or innermost zone consisting of a temperature resistant and weldable metal alloy, said latter zone having a thickness of 0.020-0.040.