GM Alternator Part Numbers and Applications


This list is for some basic configurations, what they are used on. by the
connector clock position. Both Delco and Lester part numbers are listed. Most
other brands use a P in front of the Lester application number. And if you haven’t seen a pattern here the dash number on the end is the connector clock position.

Lester is an automotive catalog service company. (They do not make alternators.) The Lester catalog system has been used for years and other companies, including AC-DELCO, will include the Lester part numbers in the “cross-reference” section of their catalogs.

10SI Alternator (63 amp)
3:00 321-39 / 7127-3 78 Chevy Camaro 350 with AC
6:00 321-135 / 7127-6 No application was found.(** See note below)
9:00 321-41 / 7127-9 79 Buick Regal 4.9L (301W) with AC
12:00 321-43 / 7127-12 77 Pontiac Grand Prix 5.7L (350R) with AC and HBL
12SI Alternator (94 amp)
3:00 321-266 / 7294-3 84 Chevy Camaro HiPo 5.0L (305G) 94amp
9:00 321-269 / 7294-9 85 Buick Riviera 5.0L (307 engine) with HD options and AC
12:00 none / 7294-12 NO AC DELCO part number or application
12SI Alternator (78 amp)
3:00 321-247 or 321-357 / 7278-3 85 Pontiac Firebird 5.0L (305H) no AC, HBL only.
9:00 321-244 / 7278-9 85 Oldsmobile Cutlass Supreme 5.0L (307Y)
12:00 321-249 or 321-254 / 7278-12 No application found

NOTE 1 – No application was found. The 6:00 position would put the two wire harness connector in direct interference with the main mounting bolt and so it is possible that no passenger cars use SI series with 6:00 positioning.

NOTE 2 – If you need a one-wire alternator most of the brands have them available. AC Delco has two types, the 10SI 72 amp is pn 321-349 with the connector at the 3 oclock position and a 15SI 105 amp unit is pn 321-667 with the connector at 12 oclock.

Delco connector clocking


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