[aceaceca]

I do not see an engine tech forum so I decided to post this here. It is quite obvious if you have been on this forum for some time that there are some members here who have significant knowledge in the engine department. Not only is their knowledge base amazing but it spans years and years of dealing with automobiles. For many, any problems that arise are just another been there, done that ,fixed that, situation and they move on to the next problem. I am not in that category by any means but I have worked on enough engines to get by. Well, I had a recent gotcha moment with my 65 GTO that has been family owned since new and serviced solely by me it's whole life. I am going to relate the problem I encountered with the engine and I am curious if one of you veteran car guys knows right of the bat what I was dealing with. I know the solution to the problem as I fixed it .

Problem: When the motor drops down to a slow idle it knocks as if a bearing were spun or a wrist pin loosened. Not a bamb bamb knock but definite audible knock. When the idle comes up a bit the knocking stops. When you hear it you think oh no, the motor is toast. What do you think was causing this?

I will give you a critical hint so you do not go off on a tangent. The cause is not in the long block.