I was putting back together my engine after replacing the water pump gasket and was trying to start it. The timing had been thrown off and I also was out of fuel. I filled up the tank and began to turn over the engine to get it to prime and while cranking it began to knock/rattle. It sounded like the flywheel had come loose. I pulled off the bellhousing and the flywheel is still bolted in firm. I pulled the oil pan and everything looks to be in order. I thought maybe something broke. The sound isn't very loud but it is noticable. Could this be a bearing that gave or what?