The timing chain position relative to the crankshaft sprocket must be maintained to preserve base engine timing when the camshafts are removed for cam, actuator, or valve service. Before the cam actuators are removed, GM-50656 retainers are clamped around the timing chain pins on both the intake and exhaust sides of the cylinder heads. The retainers are then bolted to the cylinder head to maintain the chain tension, but still allow access to the actuator bolts, to allow the cams to be serviced. On reassembly, once the actuators and camshafts are completely installed, the retainers are removed, with the chains in the correct timing position.