Upgrading Your Alternator

By Mike Yrenaya

The following is an article outlining an upgrade from an externally regulated alternator found in 1968-72 Skylarks/GSs to the later internally regulated alternator found in GM V8s of the 1970s and early 1980s.

The first step is finding the correct alt. for your application. There are two types of internally regulated alt. by GM. They are the SI series and the CS series. The SI series are typically found on cars of the 1970s and early 1980s and usually have a single groove pulley (V-belt driven.)

The CS series are found on later, fuel injected or ECM type cars and usually have a multi-goove pulley(serpentine belt driven.)

You are more likely to find an SI than a CS unit. The SI can be found remanufactured or at a salvage yard. Parts are cheap and readily available. The unit is rebuildable in the field. The CS unit is quite expensive and not rebuildable.

There are two types of SI alternators, 10-SI and 12-SI. The 10 has a 63 amp output and the 12 is 94. If your car is basically stock, the 10 will do fine. If you have a lot of power accessories, high perf. ignition, lots of gages etc., you will need a 12. There are upgrade kit availble by Quick Start which boosts the alternator output. Kits include new stator ring and diode trio. Kits are available from parts sources such as Summit Racing. If you require more output, the CS alternators are 105 amps but require pulley changes and wiring upgrades to handle the increased amperage.

The 10 and 12 can be differentiated by the cooling fins on the alt. rear. The 12 has six large cooling vents while the 10 has three smaller vents. The mounting holes and wiring is identical.

After you have found the alt., make sure yo get the wiring connectors, plastic two wire connector. These are availble at parts stores if you can not use the spade connectors of the right size. Make sure the alternator is visually okay, no excessive play on the pulley shaft, no signs of damage, stripped threads etc.

The wiring is quite simple and makes use of the wires already in place. The external voltage reg. is removed entirely from the circuit. You are then left with 4 wires originally connected to the volt reg. F,2,3,4 (note which is which with a marker or tape.) Do the following:

 1. Cut the connectors off each wire, no longer needed.
 2. White wire (2) is no longer needed. Other end at alt.
 3. Red wire (3) can be taped.
 4. Blue wire (F) and dark brown (4) should be soldered or
 spliced together. This is the exciter to turn the alt. on.

This completes the removal of the old alt. and ext. regulator. Now, let s wire the new high output alt. There are three connections: two male spade connectors with a matching female and ring post located on the rear. The two spade connectors are marked 1 and 2. If unknown, face the rear of the unit, the left one is 1 and the right is 2. Now, do the following:

 1. Solder/splice the blue wire to 1.

 2. Use a 14 gage or larger(numerically smaller) wire to go from 2 
    to the BAT ring post on the rear.

 3. Attach the orig. red charging wire to the BAT also. Ensure this 
    wire leads to the battery as this does the charging.

Mount the alt. The belt size will be the same as the old one. Start the car and read the voltmeter which should be 12-14 volts. If no voltmeter, use a multimeter to read the voltage across the battery terminals which should be 13.9-14.8. Do this test at a high enough rpm, 1600, to turn on the alt. Alt. should now be able to support all power accessories. If not, you need a higher output alt.

If you have any questions, e-mail Mike Mike