We have a 1983 Porsche 944. We just recently had a bolt go through the valve cover. The bolt is the same bolt seen holding the valve cover on. But there are no bolts missing on the valve cover. The car overheated and the cylinder head was removed approximately 1000 miles ago. Is it possible that the bolt was accidentally left in the cam housing and was okay in a safe place until it got jolted out and through the valve cover.