For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition
65 WarningCamshaft Timing Chain, Sprocket, and Tensioner Replacement Valvetrain Valvetrain Timing
Special ToolsEN-45027 Tensioner ToolEN-45059 Angle MeterEN-48953 Camshaft Actuator Locking ToolFor equivalent regional tools, refer toSpecial Tools.Removal ProcedureRemove the camshaft cover. Refer toCamshaft Cover Replacement.Remove the number-1 cylinder spark plug. Refer toSpark Plug Replacement.R ...