Patent ID: 7066123

Claim:
An internal combustion engine having intake and exhaust valves comprising: a pushrod; a rocker arm having a pivot between its ends and having one end engaged by the pushrod; a valve stem engaging the other end of the rocker arm; an adjustable stop having at least two positions for the rocker arm pivot, a lock position elevated above a rest position, comprising: an at least partially hollow member on which the rocker arm pivot is free to slide, an outer sleeve engaging the rocker arm pivot and free to slide on the outside of the member, an annular chamber between the outside of the member and the inside of the outer sleeve, a hole through a wall of the member between the inside of the member and the annular chamber; and an obstruction which permits flow or blocks flow through the hole; and a spring which is deformed before the pivot reaches the lock position, a first portion of the stroke of the spring being smoothly continuous with a relatively lower force/displacement slope and a second portion of the stroke of the spring being smoothly continuous with a relatively higher force/displacement slope.