Internal combustion piston engine includes a cylinder head partly defining two ducts and a combustion chamber, and poppet valves movably arranged in the cylinder head between positions allowing or preventing flow between the combustion chamber and the ducts. The poppet valve has a stem, a valve head having a hollow interior space, a lower surface facing the combustion chamber, an upper surface including a portion adjacent the stem, and a peripheral edge section that extends from the upper surface of the valve head to the lower surface. The valve head is formed separate from but connected to the valve stem in a manner to enclose the hollow space, for example, by a circumferential welding seam. The peripheral edge section contains an arcuate contact surface that extends from the upper to lower surfaces of the valve head and without any sharp edges between upper and lower surfaces.

A valve spring retainer for an internal combustion engine includes a body having a lower portion and an upper portion. The lower portion defines a radial flange and a first opening extending axially therethrough. The upper portion includes a first wall and a re-entrant lip. The first wall extends at least partially axially away from an outer perimeter edge of the radial flange. Together, the first wall and the radial flange define an open reservoir for receiving and retaining oil therein. The re-entrant lip extends from an outer end of the first wall at least partially radially inward toward a central axis of the first opening. The re-entrant lip extends over a portion of the reservoir defined by the first wall and the radial flange.

An iron-base sintered alloy material includes a matrix phase, Co base inter-metallic compound particles having hardness of 600 to 1200 HV, carbide-type particles having hardness of 400 to 700 HV, and optionally solid-lubricant particles, the particles being dispersed in the matrix phase. A matrix part including the matrix phase and the two kinds of hard-particles contains 0.3 to 1.5% by mass of C, and 10 to 50% by mass of one or more kinds selected from Si, Mo, Cr, Ni, Co, Mn, S, N, V, Ca, F, Mg, and O, the balance being Fe and unavoidable impurities. By dispersing, in the matrix phase, the Co base inter-metallic compound particles having high hardness, and the carbide-type particles having low hardness and low aggressiveness to mated material and increasing mechanical strength, wear-resistance can be improved with low aggressiveness to mated material and high radial crushing strength (350 MPa or more).

An iron-base sintered alloy material includes a matrix phase, Co base inter-metallic compound particles having hardness of 600 to 1200 HV, carbide-type particles having hardness of 400 to 700 HV, and optionally solid-lubricant particles, the particles being dispersed in the matrix phase. A matrix part including the matrix phase and the two kinds of hard-particles contains 0.3 to 1.5% by mass of C, and 10 to 50% by mass of one or more kinds selected from Si, Mo, Cr, Ni, Co, Mn, S, N, V, Ca, F, Mg, and O, the balance being Fe and unavoidable impurities. By dispersing, in the matrix phase, the Co base inter-metallic compound particles having high hardness, and the carbide-type particles having low hardness and low aggressiveness to mated material and increasing mechanical strength, wear-resistance can be improved with low aggressiveness to mated material and high radial crushing strength (350 MPa or more).

A gasket for a valve of an internal combustion engine is described. The valve has a guide element defining a through seat, and a stem movable in a sliding manner in said seat. The gasket has a central axis and comprises: an elastically deformable sealing element, having an annular configuration with respect to the axis and suitable to be arranged externally on the valve to cooperate both with the guide element and with the stem; a supporting member having an annular configuration, arranged coaxially on at least part of the sealing element so that the latter is pressed radially between the supporting member and the valve; an end flange projecting radially outwards from the supporting member and configured to receive the elastic load of a coil spring of the valve; and protruding means distinct from the flange, projecting outwards from the supporting member and suitable to cooperate with the spring of the valve to maintain it coaxial with the axis.

A gasket for a valve of an internal combustion engine is described. The valve has a guide element defining a through seat, and a stem movable in a sliding manner in said seat. The gasket has a central axis and comprises: an elastically deformable sealing element, having an annular configuration with respect to the axis and suitable to be arranged externally on the valve to cooperate both with the guide element and with the stem; a supporting member having an annular configuration, arranged coaxially on at least part of the sealing element so that the latter is pressed radially between the supporting member and the valve; an end flange projecting radially outwards from the supporting member and configured to receive the elastic load of a coil spring of the valve; and protruding means distinct from the flange, projecting outwards from the supporting member and suitable to cooperate with the spring of the valve to maintain it coaxial with the axis.

A method for making a valve stem seal, comprising the steps of providing a metal retainer having a top portion and a body portion. The body portion having a first section and a second section. In a first state, the first section of the body portion is cylindrical and the second section of the body portion is cone shaped. Providing a hollow mold. Inserting the metal retainer into the outer mold piece, inserting the inner mold piece into the metal retainer, and then securing the inner and outer mold pieces to each other. Filling a cavity around the top portion of the metal retainer with an elastomeric compound. Removing the metal retainer and the formed rubber sealing element from the mold pieces, and pressing downward over the formed valve stem seal to compress the second section of the body portion radially inwardly.

A method for making a valve stem seal, comprising the steps of providing a metal retainer having a top portion and a body portion. The body portion having a first section and a second section. In a first state, the first section of the body portion is cylindrical and the second section of the body portion is cone shaped. Providing a hollow mold. Inserting the metal retainer into the outer mold piece, inserting the inner mold piece into the metal retainer, and then securing the inner and outer mold pieces to each other. Filling a cavity around the top portion of the metal retainer with an elastomeric compound. Removing the metal retainer and the formed rubber sealing element from the mold pieces, and pressing downward over the formed valve stem seal to compress the second section of the body portion radially inwardly.

A rocker arm includes a pair of sidewalk disposed along a heightwise direction so as to be opposed to each other. The sidewalk define a space to house a roller and have opposed portions extending in the heightwise direction relative to adjacent portions which are adjacent to the opposed portions. The opposed portions have thinner portions having smaller thicknesses than the adjacent portions.

A gasket is described configured to be mounted on a valve of an internal combustion engine, having a central axis and comprising: an annular elastically deformable sealing element, having a radially internal surface having a first portion, adapted to cooperate with contact with a stem of the valve, and a second portion, configured to cooperate with contact with a guide element in a sliding manner of the aforementioned stem; and an annular support member, arranged coaxially on at least part of the sealing element so that the latter is pressed radially between the support member and the valve; the second portion has a circumferential surface section and a plurality of discrete bumps, projecting cantilevered from the circumferential surface section so as to cooperate with contact in use with the guide element, angularly spaced from each other around the axis and forming a discontinuous undulation of the radially internal surface.