Typical internal combustion engines include one or more intake and/or exhaust valves at each cylinder in the cylinder head. Means are provided to permit quantities or air/fuel mixtures to enter a combustion chamber. The exhaust valves open to allow combustion products to exit the combustion chamber. The timing of the opening and closing of these valves, and the area of the exhaust space between the chamber and the valve when opened are variables which are mechanically adjusted to obtain good fuel burning and maintain appropriate pressure in the combustion chamber. The valve stems extend outward through the cylinder head. Resting on or above the external end of each valve stem is one end of a pivotally mounted rocker arm. A second end of the rocker arm is operatively connected to a push rod and/or a cam shaft. Movement of the push rod or cam shaft causes the rocker arm to move in an actuate path (rock) around its pivot point, in turn pushing the valve stem downward, causing the valve to move down (open). A spring arrangement typically causes the valve to close when the rocker arm rotates upward away from the valve stem. The amount of movement of the valve, and its ability to seal the chamber, is usually controlled by adjustment of an adjustment screw (valve adjuster stem) and locking nut (valve adjuster lock nut) combination, also referred to as tappet adjustment, mounted within the end of the rocker arm and in contact with the top of the valve stem or the push rod or both as the arm rotates downwardly.
One of the fundamental problems in adjusting valve clearance is the difficulty of manipulating the adjustment screw and locking nut, particularly because of the confined space in which the mechanic must operate and the tendency of the adjustment screw to move during tightening of the locking nut. Typically, the locking nut must be grasped by a wrench, loosened and held in that loosened position while the screw is adjusted and a gap between the valve stem and screw bottom is being set using a gap gauge. The nut must then be tightened while the screw is held fixed so the adjustment (the desired gap) does not change.
U.S. Pat. No. 4,229,999 to Rottigni describes a valve adjustment tool which includes an elongated barrel having a bore therethrough, an externally threaded upper barrel and an integral collet which forms a valve lock nut socket on the lower end of the barrel. The collet is surrounded by a compression collar. An elongated internally threaded sleeve is placed over the barrel abutting the compression collar. Threading the sleeve downward on the barrel compresses the collet. An elongated valve adjuster driver is placed through the bore of the barrel. This driver has a large disc shaped knob at its upper end and an engagement lug at its lower end. When assembled the collet locks on the adjustment nut so that the nut can be loosened and tightened and the driver is used to turn the adjustment screw.
U.S. Pat. No. 1,544,520 shows a one piece tool for simultaneously grasping the locking nut and turning the adjustment screw.
U.S. Pat. No. 2,601,796 shows a third example of a tool used for tappet adjustment. It includes a sleeve member for gripping the locking nut, a hollow socket member which slides onto and grips the shaft of the sleeve member and a screw driver placed through the center of the socket member to engage the adjustment screw. The sleeve member is held stationary during the adjustment process by a conventional box wrench.
Each of these prior tool assemblies have multiple components that make the adjustment process cumbersome. The valve adjustment tool described herein simplifies the adjustment process and allows the user to simultaneously measure, adjust clearances and lock the tappet assembly in the new adjusted state. A user can untighten and tighten a valve stem lock nut and adjust and simultaneously measure clearances without removing the tool from engagement with the lock nut during the adjustment, measuring and locking procedure.