Extreme 4 Wheelin' - Tech
GM Alternator Info.

The most common charging system upgrade/modification is adding or converting to a GM style internally regulated alternator produced by AC-Delco. The most common varieties are listed in TABLE 1.

Some of the main advantages are easy availability, plus common mounting and wiring. There are some slight variations of both, but this table lists models from each series that are mostly interchangeable (common 6.6" 180 degree mounts, overall case sizes will vary).   SI units shown are standard 3-wire hookup, CS units require plug adapters.


(Common Mounting)


Example Vehicle (V groove pulley)

Lester Numbers


~ Reman Price (core)


78 Cutlass Supreme V8-260

7127 (63A)


$35 (10)


83 Chevy Cavalier 2.0L

86/87 Buick Regal V8-307 (metric threads)

7271,7272,7273 (78A)

7294 (94A)


$65 (30)

$100 (25)


81/83 Chevy Camero 5.0L


70 -105

$60 (30)


86-90 Chev, GMC, P series van 6.2L

7287 (120A)

108 - 120



88/89 Pontiac Firebird 5.0L (no pulley)

88 Chevy Caprice 5.0L (1V)


7808, 7888

100 - 105

$70 (45)

$70 (30)


93 Caddy RWD, 5.7L V8 (serp pulley)

8112 (140A)


$120 (70)


By far the most common alternator ever produced is the 10SI ("System Integrated"), with the 12SI being an upgraded version by means of better cooling (noted by a plastic fan) to handle higher current outputs. The 15SI and 17SI are physically larger units, but still share the basic 6.6" mounting center to center that was used back to the 10SI (and before).

SI series connector wiring pin-out:

The infamous '1 wire' alternator is based on the 10SI or 12SI units and require only the #2 terminal (sense) line to be connected to the output post.   These units detect the rotation of the alternator to turn the field on, therefore don't require the switched power on the #1 terminal.  Typically these are used on implement applications, or have had aftermarket regulators installed.  Generally, you are better off staying with the more common '3 wire' units.

Latest series to be introduced is the CS ("Charging System") 130 or 144 (for 130mm  or 144mm stator). The CS130 has a lower max output than the 15/17SI, but better low speed output with less noise. However, I have read that the CS130 is not all that strong, and does have reliability problems. Specifically, with cracked back cases related to belt loading.  CS130's are slightly smaller than the 10SI, but MOST (there are exceptions) use the same 180 degree 6.6" mounting.

CS144 is the size of a 15/17SI with an impressive 124-145 Amp output capacity. These are the current 'beast' alternators available on the latest high demand vehicles. Like the CS130's, there are some models with different mounting pattern from the SI norm.  I am not aware of any available units using a single 'V' groove pulley.  However, pulleys are interchangeable from 10SI thru CS144 (fans are NOT).

CS series wiring pin-out:

The following adapters are available to go from SI wiring to a CS alternator:

AC Delco: 8077
Haywire: 2110
Painless Wiring: 30707

The switched 'light' (terminal 1 on SI or 'L' on CS), must have 12V switched power with between 35 and 350 ohm resistance (typically the light itself). If below 35 ohm, the CS units will fail. I have read that switched power (no resistor) can be connected to the 'F' terminal instead,  where there is supposed to be an internal resistor. I've not confirmed this, so be ware.


10si.jpg (8136 bytes) Delco 10SI Series
61 Amp, 12 Volt, CW, 1-Groove Pulley
Used On:
(1985-73) Buick, Cadillac, Chevrolet, GMC, Oldsmobile, Pontiac 4, 6, 8 Cyl
Delco 1105360
Lester Nos:
7127, 7128, 7282
12si.jpg (9444 bytes)  

Delco 12SI Series
78 Amp, 12 Volt, CW, 1-Groove Pulley
Used On:

(1989-83) Buick, Cadillac, Chevrolet, GMC, Oldsmobile, Pontiac 4, 6, 8 Cyl.
Delco 1100250, 1105370, 1105372 & others
Lester Nos:
7271, 7272, 7272R, 7273
M8 x 1.25 Threaded Adj. Ear

12si.jpg (9444 bytes) Delco 12SI Series
94 Amp, 12 Volt, CW, 1-Groove Pulley
Used On:
(1987-84) Buick, Cadillac, Chevrolet, GMC, Oldsmobile, Pontiac 4, 6, 8 Cyl.
Delco 1101308
Lester Nos:
M8 x 1.25 Threaded Adj. Ear
cs130.jpg (10133 bytes) Delco CS130 Series
Amp, 12 Volt, CW, 1-Groove Pulley
Used On:
(1990-88) Buick Estate Wagon 5.0L
(1990-88) Cadillac Fleetwood Brougham (RWD) 5.0L
(1990-88) Chevrolet Caprice 5.0L
(1990-88) Oldsmobile Custom Cruiser 5.0L
(1989-88) Pontiac Safari Wagon 5.0L
Delco 1101229, 1101275, 1101292
Lester Nos:
7808, 7888
cs144.jpg (9355 bytes) Delco CS144 Series
140 Amp, 12 Volt, CW, 6-Groove Pulley
Used On:
(1996-94) Buick Roadmaster 5.7L
(1996-93) Cadillac Fleetwood Brougham (RWD) 5.7L
(1996-93) Chevrolet Caprice 4.3L, 5.7L
(1996-95) Chevrolet Impala 5.7L
(1995-92) Chevrolet Lumina APV Van 3.8L
(1995-92) Oldsmobile Silhouette 3.8L
(1995-92) Pontiac Trans Sport 3.8L

Delco 10479891, 10480201
Lester Nos:

Helpful Alternator Links

General alternator info:  http://www.4alterstart.com/alternators/

Find out what a vehicle model had:  http://www.olyonline.com/PPR%20Application.pdf

Cross Reference various alternator numbers: http://web2.wai-wetherill.com/new/crossref.cfm

How to tell a 10SI from a 12SI and more: http://www.madelectrical.com/electricaltech/delcoremy.shtml