[Rick Parker]

The picture did not open for me either but I can imagine small 1/3 circular bright marks in the valve reliefs. Its doubtful the rods are hurt as it would rock the piston if it was a very minor interferance or it would have been quite audible (ie: loud) and never driven after initial startup. I have seen too where on occasion if the engine is over reved the rods will momentarily strech and allow the valves to hit the piston. This is why a specific minimum clearance is set depending on application, valve springs, anticipated RPM etc.
Example: I had a Datsun 510 AutoX car several years ago with a real well built OHC 1800 13:1 domed Venolia pistons, (2) 45 DCOE carbs big cam, crank fired ignition 8000+ RPM engine. Fun car to drive. I missed a shift once and buzzed it to about 8500-8700. It immediatly began to run poorly on only 3 cylinders. I thought I had bent a valve but realized it didn't have any bad mechanical noises. After investigation what had happened was the rod had stretched momentarily and hit the ground electrode on the plug and closed it up. After replacing the plug it ran fine.