For valves to open at the proper time, which marks must be aligned?

For valves to open at the proper time, the timing marks must be aligned. Timing marks are specific indicators on the crankshaft pulley and camshaft that serve to synchronize the rotation of these two components during engine operation. When the timing marks are aligned correctly, it ensures that the camshaft, which controls the opening and closing of the valves, is in the correct position in relation to the crankshaft, allowing for optimal engine performance.

Misalignment of the timing marks can result in serious engine issues, such as valves opening at incorrect times, leading to poor engine performance, pre-ignition, or even engine damage. The timing system is crucial in four-stroke engines, where precise timing between the crankshaft and camshaft is essential for efficient operation and power generation.

Other marks, like compression marks, valve spring marks, or fuel injector marks, do not play a direct role in regulating the timing of the valve openings relative to the engine cycle; therefore, they are not relevant to ensuring that the valves open at the correct moment.