Your cam has a white zero on it and a zig-zag symbol. Opposite the zig-zag symbol, there should be a hole in the cam. If you were able to lift the cam out of the machine, you should see a pin underneath that the hole is seated on. If you look at the YouTube video that OurWorkBench posted, you will see what I'm referring to. In that video, his white zig-zag mark is at the bottom and not at the top like yours. Could the problem be as simple as the cam is seated incorrectly? Your machine was supposedly built between 1967-1972. Other people say it sews like a dream.