The camshaft actuators must be removed from the camshafts during timing chain or camshaft service, and the camshafts' relationship to the timing chain must be maintained when the actuators are removed or reinstalled. GM-51367 installs onto both camshafts and holds the assembled hex on both cams to maintain their relationship during timing chain, actuator, camshaft, or valve service. Once the engine is placed with cylinder one at TDC (compression stroke), GM-51367 is installed onto both camshafts to hold them and prevent chain jump when the actuator bolts are removed or installed. It also allows the timing chain to be replaced and re-establishes the cams in the correct position after camshaft or valve service.