I have a Briggs and Stratton 32000 engine. It has been recently rebuilt. The connecting rod is .10 under and the crank was machined to match it. The Machine shop used my .10 under rod to machine the crank. Before I started it I checked the oil and it was full SAE30. Anyway I started it up and ran it for about 20 minutes and it started to surge really bad like the carb was dirty or it was out of gas. I shut it off and filled it up with gas and started it back up it ran fine for about 30 seconds then it started to surge again. This time I started to hear a slight knock so I opened the hood and raised and lowered the rpms to see if the knock was still there. I idled it back down and then it stopped abruptly. The engine was locked up. I pulled it apart and found this. (see pictures) How could this have happened? The oil was fresh and full before and after it locked up. The connecting rod is brand new and the crank was machined to match. I can't install the rod the wrong way because if you do it will hit the camshaft. Also the Briggs and Stratton Manual shows what way to put it in. The piston and rings are also fresh and still in decent shape. What could have caused this to happen I do not think it overheated because all the shields were in place and it ran great. Any help would be appreciated! Thank you all very much!