[old_master]

It's possible that the distributor bushings are worn, but without specialized test equipment, you'll never be able to confirm that's the problem. If you hear a snap, you might be hearing spark arcing somewhere. Take a spray bottle with water and direct a mist over the distributor cap, ignition coil and wires, especially #6, (rear plug passenger side). If you do it at night, the arc will be much easier to see. Post your findings.