It depends on the kind of damage. If a piston has broken up or a valve is burned, the damage will continue to get worse until it breaks more engine parts.If only a head gasket needs replacing, that could be fixed and the engine may be serviceable again and dependable. You need to make a decision for yourself about keeping the car or junking it. Using a 5/6 engine will not be a rewarding experience. The engine will be weak, will pollute more and fail any smog test. This car's days are numbered.