In the mid '70s, GM began offering its SI-series (Systems Integrated) alternators, which not only delivered more amperage but did away with the externally mounted voltage regulator and its messy wiring. Installation is simple and the appearance has a factory look. Check out how we installed a Delco-Remy 12SI alternator on our '70 Chevelle (which formerly had an externally regulated alternator) using a wiring kit from MAD Enterprises. If your application varies, don't fret; MAD offers a variety of wiring diagrams and kits to ease installation on most any musclecar--including Ford, Mopar, and AMC muscle machines!
For about $25 you can score MAD Enterprises' alternator wiring kit (PN ALT-1) and ease the installation of a more modern factory-type Delco-Remy 10SI or 12SI alternator. The kit includes items such as a special connector and terminals for the alternator, heavy-duty 8-gauge TUFF-WIRE, wire terminals, shrink tubing, a fusible link, an inline diode (not required for all applications), and an easy-to-follow instruction booklet complete with wiring and troubleshooting tips.
The appearances of an SI-series alternator (left) and a vintage '60s DN-series alternator are similar--yet their rated output is much different. While a DN-series alternator struggles to produce 40 amps, most 10SI alternators deliver a steady 63-amp power supply, and some 12SI units churn out a whopping 94 amps. Although pulleys are similar, a 10SI comes with a metal cooling fan, whereas the 12SI has a larger plastic fan. Our stock alternator (right) has an aftermarket underdrive pulley, and, if desired, pulleys interchange between DN- and SI-series alternators.
The SI- (left) and DN-series alternators have different style plug-in connectors (arrows). On 10SI/12SI units, the rectangular plug locations are labled 1 and 2, whereas the DN-series uses a more square connector port labeled R and F. Out back, a 12SI has much larger cooling vents than a 10SI, and a 10SI has more cooling vents than an older DN-series alternator. Besides having a higher amp output, SI-series alternators also begin charging at much lower engine rpm (which is beneficial when cruising, for example) than older-style alternators.
The stock DN-series alternator uses a bracket that serves as both a mount and a ground. A similar mount/ground is needed for the new 10SI/12SI alternator. Our stock mount was close to correct for a 10SI/12SI, but had the ground bolt in the wrong location. We drilled a new 11⁄32-inch hole, used a few washers for spacers, and threaded-in a new M8x1.25x30 retaining bolt. If you want the correct bracket for the conversion, order GM PN 14079285.
Convert the DN alternator's two-wire connector to the new SI-type connector (supplied). If they're in good shape, you can reuse the old terminals. However, our stock wire-ends were tattered near the connector, so we cut the wires about an inch away from the terminal.