What is inserted into the cylinder head to help valves seal and transfer heat?

The component that is inserted into the cylinder head to help valves seal and transfer heat is valve seats. Valve seats are critical for the proper functioning of internal combustion engines, providing a surface for the valve to close against, ensuring a tight seal when the valve is closed. This seal is essential for maintaining compression within the cylinder and preventing gases from escaping during the engine's operation.

In addition to facilitating a proper seal, valve seats are designed to conduct heat away from the valves. This heat transfer is crucial because the valves operate at high temperatures due to the combustion process, and effective heat dissipation helps to prevent valve warping or failure. By ensuring a good fit and heat transfer, valve seats contribute to the engine's overall efficiency and performance.

In contrast, spark plugs ignite the air-fuel mixture in gasoline engines, valve springs are responsible for closing the valves after they are opened, and push rods transmit motion from the camshaft to the valve lifters. While each of these components plays a vital role in the operation of an engine, they do not directly relate to the sealing and heat transfer functions provided by valve seats.