Fabricating internal combustion engine cylinder heads with close tolerance internal surfaces

Abstract

A method for fabricating an internal combustion engine cylinder head, comprises the steps: (a) forming a cast cylinder head with a passage having implanted in the walls of such passage a valve stem guide sleeve insert and a valve seat insert, the inserts being formed of fused powder metal and each having an internal cylindrical surface prepared to near net shape no longer requiring macroscale sizing; and (b) microsizing both of the internal cylindrical surfaces by a single pass of a common rotary abrasive tool inflexible along its axis and supported for accurate alignment independent of the guide sleeve. The cylinder head may be first formed with such passage having a recess for a valve seat insert and a guide bore for a guide sleeve; preshaped inserts are then press-fit into such recess and guide bore. Near net shape means an overside tolerance of plus 0.002-0.003 inches; macroscale means measurements in increments or units greater than 0.01 inches.

Dependencies are inferred from the claim text.