It appears the reason of the bent valve is it hit the top of the piston. How is this possible? I set the timing chain as indicated in the manual. Piston at tdc, matched timing chain marks to marks on crank and cam gear, both valves were closed. Cam gear pin at top and crank mark as the same position as in the manual. I'm certain this was set correctly as I checked and rechecked about 10 times before I put the front cover back on because I was uncertain about the timing and wanted to make certain it was set right. Your thoughts appreciated. I'm getting fed up with this vehicle and my wife is threatening to divorce me if I don't do something about this truck, spent all spring working on this thing and it's not like I haven't been inside this engine before (overhauled and changed heads). What can you say!!!