Abstract: An intake valve includes a floating seat for attaining variable valve timing. A valve stem is integral with a valve head base. The valve head base includes a region for accommodating a peripheral ring in vertically-actuable relationship. The region of the valve head base for accommodating the peripheral ring includes a vertical locking portion and an upwardly-convex portion that mates with an downwardly-concave portion of the interior of the peripheral ring. A port may be arranged to vent gases at an upwardly-sloping portion of the bottom of the interior of the peripheral ring, thereby preventing instantaneous gas seepage while the peripheral ring is elevated. The vertical locking arrangement is positioned at the inner circumference of the peripheral ring to permit adjustment of peripheral ring travel without adding to the mass of the valve head.