This is just a quick visual identification guide for Delco type alternators.
First Alternator used on GM Vehicles to replace old DC Generators. External regulator mounted on the firewall. First used in 1963 on the Corvette.
First internally regulated alternator used by GM. Replaced the externally regulated 10DN. Again, first used on the Corvette. Wasn't into full production until about 1962.
The 21Si and 22Si are near identical cosmetically. Internal differences are...
Upgraded from the 10Si and 12Si.
A retooling of the flaws found in the original CS130.
Upgrade from the 15Si and 17Si. Same Bolt Pattern.
Used an upgraded bearing and battery post assembly