Which item is designed to keep engine valves closed?

The item designed to keep engine valves closed is the spring. Valve springs are essential components in the engine's valvetrain system. They exert force on the valves, ensuring they remain closed when they should be. This closure is critical for maintaining the engine's compression and ensuring that the air-fuel mixture does not escape from the combustion chamber during the compression stroke.

When the engine operates, the camshaft rotates, pushing against the rocker arm (or lever) that acts on the valve. This action compresses the valve spring and allows the valve to open at the appropriate timing for intake or exhaust. Once the cam lobe passes, the spring force then closes the valve, sealing the combustion chamber. The correct timing and proper function of the valve springs are crucial for engine efficiency, performance, and overall operation.

The other components listed do not serve the purpose of keeping the engine valves closed. While head studs help secure the cylinder head to the engine block, pushrods transfer movement from the camshaft to the rocker arms, and rocker arms assist in opening and closing the valves, it is the valve springs that perform the essential role of maintaining closure when the valves are not in operation.