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.

Internal combustion engines having multi-stage telescoping poppet valves in lieu of conventional poppet valves are disclosed. The engines may have pistons with a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The piston heads may include one or more depressions and may be domed to facilitate the movement of air/charge in the cylinder. The engines may also have non-circular, preferably rectangular, cross-section pistons and cylinders. The engines also may include a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.

A valve stem seal assembly has an elastomeric seal with first and second radially inwardly directed sealing lips that are in intimate sealing contact with a valve stem. The assembly also has a metal seal retainer with a first metal seal retainer portion that has a surface axially slanted inward and downward from a top of the elastomeric seal. This slanted portion forms a metal frustoconical foundation with a second metal seal retainer portion that directly radially extends from the metal frustoconical foundation. The axially slanted inward surface of the metal retainer is directly radially outward from the radially inwardly directed first sealing lip.

A valve stem seal assembly has an elastomeric seal with first and second radially inwardly directed sealing lips that are in intimate sealing contact with a valve stem. The assembly also has a metal seal retainer with a first metal seal retainer portion that has a surface axially slanted inward and downward from a top of the elastomeric seal. This slanted portion forms a metal frustoconical foundation with a second metal seal retainer portion that directly radially extends from the metal frustoconical foundation. The axially slanted inward surface of the metal retainer is directly radially outward from the radially inwardly directed first sealing lip.

Internal combustion engines having multi-stage telescoping poppet valves in lieu of conventional poppet valves are disclosed. The engines may have pistons with a skirt with a field of pockets that provide a ringless, non-lubricated, seal equivalent. The piston heads may include one or more depressions and may be domed to facilitate the movement of air/charge in the cylinder. The engines may also have non-circular, preferably rectangular, cross-section pistons and cylinders. The engines also may include a split crankshaft. The engines may use the pumping motion of the engine piston to supercharge the cylinder with air/charge. The engines also may operate in an inverted orientation in which the piston is closer to the local gravitationally dominant terrestrial body's center of gravity at top dead center position than at bottom dead center position.