As nuts as it sounds any mechanic can tell you for decades GM insisted on placing an inside/outside tooth star washer on the negative battery cable between the cable lug and the alternator mounting bracket.
But then GM pioneered the use of copper plated aluminum battery cables. With side terminal group 72, 74 and 77 batteries and alternators that used the Delco 1116405 voltage regulator with a 15.0 volt set point. Yeah, aluminum slapped up against a battery terminal. Battery cable replacements like Deka and Whittaker, made a fortune.
