When the Timing belt brakes does it damages valves in a Oldsmobile Silhouette?

Yes, a broken timing belt in an Oldsmobile Silhouette (and most interference engines) will almost certainly cause valve damage. Oldsmobile Silhouettes used engines with interference designs, meaning the pistons and valves share the same space in the cylinder. When the timing belt breaks, the valves are no longer synchronized with the piston movement. This often leads to bent or broken valves as the pistons collide with them.