My 468, mild camed engine runs fine and has good power with the 4 SPD, 342 gears. The issue is it has a knock that does not go away for all the 5 years I have owned the car and 5-6 hundred miles. I have done nothing to the engine as it was "rebuilt" when I bought the car. If it is a "rod" how do I know and what is the easiest way to fix? If not what could it be?