Is there another way to determine tdc besides lining up the mark on the rotor? The reason I ask is because the rotor on this 80 special I am working on is new and there doesn't seem to be a clear mark. I adjusted the valves using what I believed to be the mark, but it is difficult to see, and is a very small, but seems to be a clear endent on the edge of the rotor. The reason I am not completely sure about the mark is because there seems to be slightly more noise from the valves, like the gap is off, when the engine is running. Thanks