The Cummins tappet cover is a vital part of the engine, and its part number is 3918753. It's an important component that helps to protect the valves from dust, dirt and other debris. It also helps to keep oil inside the engine so it can lubricate the moving parts properly. The tappet cover should be inspected regularly for signs of wear or damage, and replaced if necessary. This will help ensure your engine runs smoothly and efficiently at all times. If you're unsure what size or type of tappet cover you need for your vehicle, check with your local auto mechanic or Cummins dealer who can tell you which one is right for you.