Adjust Rocker Arms on a Mopar Big Block
Unlike the majority of engines, where each individual rocker arm is mounted onto its own pedestal, big-block Mopar engines use two shaft-mounted rocker arm assemblies. Each assembly consists of a tube inserted through eight rocker arms. This shaft-mounted design provides greater stability to the cylinder head and to the valvetrain than pedestal-mounted rocker arms, particularly at high engine speeds. Fortunately, big-block Mopar rocker arms can be quickly adjusted without disassembling the shafts.
Instructions
1. Turn the engine on and allow it to idle for thirty minutes at a fast idle speed to stabilize the engine temperature.
2. Turn the engine off, then remove the valve covers from the top of both cylinder heads. Each valve cover attaches to the cylinder head with six bolts, which must be removed with a wrench. Two of the bolts are located at the top of the valve cover, and four bolts are located at the bottom of the valve cover.
3. Locate each rocker arm's adjusting bolt. At the back of each rocker arm, where the pushrod touches the bottom of the rocker arm, is a single bolt called a cup end adjuster. Turning this bolt adjusts the rocker arms. Note that a hex head wrench, sometimes referred to as an Allen wrench, must be used to turn the cup end adjuster.
4. Turn the engine on and allow it to run at its idle speed.
5. Twist the cup end adjuster for one rocker arm in a counterclockwise direction only until the rocker arm starts to produce a clacking sound, then slowly tighten the cup end adjuster until the clacking sound stops.
6. Turn the cup end adjuster in a clockwise direction one-quarter of one turn to finish the adjustment process for that valve, then repeat the process for the remaining 15 valves.
7. Turn the engine off and bolt the valve covers to the cylinder heads with new valve cover gaskets.
