The Build Sheet code for the alternator on my '71 Pontiac Grand Safari with the original 455 is "SP," but I can't find which alternator this represents online. I need it in order to order new belts so I can reassemble my car. Anyone know if SP stands for the 80amp alternator?
The build sheet code is meaningless in this discussion. You need the belt for what type of alternator you have. There were 2 types of alternators and they were differentiated by case style. The 37-63A alternator was the standard 10SI alternator that most Pontiac engines came with. If you got certain options such as the rear defroster, you were given the HD alternator which was an 80A unit and it has 2 tabs on one side of the case, plus a different set of brackets. You can see both of them in the attached photos. Unless you have the alternator that has the extra bracket and larger case, you need the standard 10SI alternator belt that any Pontiac v8 from 1969-1979 used which is around 48" circumference. Otherwise you need the 80A one that is approximately 51.5" circumference.
I'm thinking the 80A had a 'rear' plug for the F/S wire connector; I had a former friend who had the 80 amp on a 455 he unloaded from a '73 Grandville he parted out. So if I'm correct, that should help specifically ID Vette's alternator.
Considering no new castings of the cases have been done, all cases should have the markings. When amp options were listed, that's how the auto parts store and rebuilders determined what the amperage was.
