was playing around with my new Borescope imitation and was looking inside my #1 cylinder and found this depression/mark/whatever it is on top of the piston. Is this a cause for concern? or should I just ignore it? Sorry for the crappy quality. According to the PO the engine has been "rebuilt", ya right.

 

Still runs right? no funny sounds? A mark like that should not effect anything. If you were on the gas racing and making that engine put out max power for a long time it might make a hot spot... but other then that run it. I have taken a grinder and lobbed off glow plugs smashed in to a diesel piston, ground out valve punches and just slammed the heads back on and down the road.