How does a broken timing belt affect an interference engine?

In an interference engine, the design allows for very close tolerances between the moving parts, particularly between the pistons and the valves. A broken timing belt in such an engine can lead to a catastrophic failure. When the belt snaps, it disrupts the synchronization between the crankshaft and the camshaft. This means that while the crankshaft continues to turn, the camshaft no longer positions the valves correctly. As a result, there is a risk that the valves will remain open when the piston comes up, leading to a collision between the pistons and the open valves. This collision can cause bending of the valves, damage to the pistons, and potentially other significant internal engine damage.

In contrast, while a non-interference engine has enough clearance that if the timing belt fails, the pistons and valves do not collide, the interference engines are specifically designed such that a broken timing belt can lead to serious issues and costly repairs. This highlights the importance of regular maintenance on timing belts, especially for vehicles with interference engines.