A broken timing chain implies the valvetrain and crankshaft are no longer in sync, possibly causing the pistons and valves to strike each other. This collision may cause damage to the valve train, cylinder walls and cylinder heads. The extent of the damage from the interference depends on the engine speed and load at the time of failure.
An engine mechanic can evaluate the condition of the valvetrain and cylinder heads to ascertain if the damage is limited to timing components, allowing for a rebuild, or if the engine must be replaced.
