Final answer:
The valve stem seal belongs inside a cylinder head and helps prevent oil from entering the combustion chamber.
Step-by-step explanation:
The valve stem seal belongs inside a cylinder head. The valve stem seal is a small ring that is placed around the valve stem, which helps to prevent oil from entering the combustion chamber of an engine. It ensures that only air and fuel mixture enters the chamber during the combustion process. Without a proper functioning valve stem seal, oil can leak into the combustion chamber, causing issues such as excessive smoke and loss of power.