Story: The 1980 has to sit outside for the winter. I told my son to get it running every couple of weeks to keep the battery charged.

Last time he goes out the engine is making the most horrific knocking noise. It is definitely on the top of the engine. I asked a local shop what he thought it might be? His idea is a piece of carbon came loose in the engine. His recommendation, get it running rev it up some and pour a steady stream of ATF fluid into it. He said it should break up the carbon.

Has anyone ever done this? Also, the son is a little disappointed. He was hoping that we might have the chance to rebuild the engine. Something neither he nor I have ever done.