An engine has a cylinder head defining an intake port with a roof defining first and second valve guide bores upstream of first and second siamesed intake valve seats for a cylinder. The head has first and second asymmetric fairings extending outwardly from the roof and positioned directly upstream of respective bores. Each fairing has an inner wall intersecting an outer wall along an upstream edge and an inclined planar roof wall extending between the inner and outer walls. A method of forming the cylinder head and engine is also provided by milling the fairings from a roof preform formed with the intake port of the head.

A piston has a piston crown and a top land extending circumferentially around the piston crown, as well as a combustion bowl and at least one valve pocket machined therein. The valve pocket has a side wall and a bottom, and wherein the side wall extends at an angle of between 110 and 120 from the bottom. A method for forming such valve pockets in the piston crown includes machining the valve pockets with a rotating cutter having an inverted frustoconical shape such that an angle between a bottom of the cutter and a side wall of the cutter amounts to between 110 and 120.

In order to adjust the volume of the combustion chamber with high accuracy, a cylinder head 200 includes a recess 204 constituting part of the combustion chamber of the engine and a mating surface for a cylinder block. The recess 204 includes a plurality of openings to which a plurality of specific members are attached respectively. The mating surface 202 is formed to have a cutting stock with respect to three-dimensional shape data of the cylinder head 200 designed to have a target combustion chamber volume. The adjusting method further comprises measuring the surface shape of the recess and the shape of the mating surface around the recess by successively changing the irradiation position of a laser beam using a line laser displacement meter. The adjusting method further comprises removing data of regions equivalent to the plurality of openings from measurement data by comparing the measurement data obtained by the line laser displacement meter with the three-dimensional shape data. The adjusting method still further comprises: calculating the volume of the recess 204 based on the measurement data from which the regions equivalent to the plurality of openings are removed; and deciding the cutting amount of the mating surface 202 by comparing the calculated volume of the recess 204 with a volume of the recess 204 based on the three-dimensional shape data.

A milling tool is disclosed. The milling tool may include an elongated body having a longitudinal axis and a plurality of cutting inserts. The cutting inserts may each have a cutting edge and a cutting radius and be coupled to the body and spaced along the longitudinal axis. One or more of the plurality of cutting inserts may be adjustable (e.g., mechanically adjustable) between first and second cutting radii. A difference between the first and second cutting radii may be at least 10 m. The milling tool may include cutting inserts having a plurality of different cutting radii. The milling tool may be configured to have a length that spans an entire height of an engine bore. The cutting inserts having different radii may compensate for dimensional errors in an engine bore diameter that occur when milling a deep pocket.

Milling tools configured to increase surface roughness are disclosed. The tool may include an elongated body having a longitudinal axis and a plurality of cutting inserts coupled to the body and spaced along the longitudinal axis, each cutting insert having a cutting edge. In one embodiment, the cutting edges may have an orientation that is oblique to the longitudinal axis of the elongated body. Each cutting edge may have a first end having a greater cutting radius than a second end. The cutting edges may be offset from the longitudinal axis of the elongated body by an offset angle. In another embodiment, the cutting edges may have a textured or rough surface profile. For example, the cutting edges may have a mean roughness (Rz) of at least 7.5 m. The milling tools may increase the surface roughness of a milled engine bore to facilitate a subsequent rough honing process.

A method of milling an engine bore is disclosed. The method may include inserting a milling tool having a plurality of cutting edges along a longitudinal axis into an engine bore, rotating the milling tool about the longitudinal axis and moving the milling tool around a perimeter of the engine bore to remove material from the engine bore, and rough honing the bore. The milling may generate a tapered bore (e.g., frustoconical). The rough honing process may increase a minimum diameter of the tapered bore by at least 60 m. A total time of the milling and honing process may be less than 60 seconds. In one embodiment, the honing step may include using a grit size of at least 200 m and/or using a honing force of at least 200 kgf. The method may reduce the cycle time and tooling requirements of forming engine bores.