My timing chain broke and destroyed all the gears and also broke the cam shaft and one cam bearing. I sent the head out and had four valves replaced after I saw the pistons were okay. Got it all together and set #1 at TDC and aligned the cam shaft groove with the mark on the gear; pulled the pump out and set the timing at 25 degrees BTDC. To my surprise as soon as I had the air out of the fuel lines at 10 degree s temperature, it started right up. Problem, it ran for one minute and than quit. Thinking there wass some air in the lines, I tried to start it twice more. l It ran for a few seconds. Than on the third attempt, I heard noise. Valve cover was cracked. Took it off and the cam shaft was broke again and two cam bearings. Valves were set intake .004 and exhaust .016. Setting the timing and valves, I rolled the engine over at least 25 times with a socket on the fly wheel and there was nothing holding it. Any ideas what I did wrong?