The only time I ever saw a timing chain jump was back when I was a kid. I was tuning my 56 Victoria. I had used a piece of coat hanger for throttle linkage. I revved the engine and my throttle stuck wide open. We got scared and ran off. I finally came back and shut off the key. The timing chain was spaghetti after that.
Seriously, check the simple things first like points, condenser, wires and coil. How old is your gas tank? The carb would be the last thing I would check, but it could be full of dirt.
