It appears that you’ve provided information about a Cummins 6BT lower main bearing with part numbers 3978820 and 3978818. This main bearing is designed to fit the Cummins 6BT engine and is manufactured in China to OEM standard size. It’s an essential component in the engine’s construction, contributing to its smooth and efficient operation. Main bearings like this help support the crankshaft and maintain proper clearances within the engine.

Please note that accurate and reliable engine parts are crucial for the overall performance and longevity of the engine. Always ensure that you source parts from reputable suppliers and manufacturers to guarantee quality and compatibility with your Cummins 6BT engine. If you have any specific questions or concerns about this main bearing or its application, feel free to ask.