I have a Tecumseh OHH50 68002F 5.5 HP engine on a wood chipper that just dropped a valve. The little retainer ring had cracked and let it drop into the cylinder. I am getting a new head for it and would like to just go with that if possible however the top of the piston is scarred from the valve banging against it before it came to a stop. There is no hole in it. Can I safely run the engine with the damage to the top of the piston or do I need to replace it as well. Obviously, that would involve more cost and a lot more labor as well. Any input would be greatly appreciated.