I just replaced the timing belt, but I think there is valve and piston damage.
Your Subaru Forester comes equipped with a boxer engine that is often referred to as an interference engine. An interference engine means that the pistons and valves inside occupy the same space but at different times during operation. The timing belt is what keeps these components from colliding together. When the timing belt fails, it is then likely that the pistons and valves occupied that same space and caused damage.
In most cases the pistons can be reused and bent valves can be replaced. However, I have seen when the force of the two colliding can actually crack the pistons. Cracked pistons would be a worst case scenario, requiring a full engine rebuild to repair. Bent valves means the cylinder heads will have to come off so the repair can be performed. Once the cylinder heads are off the pistons can be carefully inspected for damage. A certified mechanic will have the proper tools to determine if you have one or more bent valves, or if your pistons are cracked.
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