I did this swap on my truck, but it directly relates to a C3 so I am posting it here. I recently installed dual C4 fans on my '83 K20 pickup, same setup I have on my Vette. Speed density Tuned-Port and these dual fans. On the Vette I have an '84-85 C4 alternator. It is an SI type 110 amp but has some internal changes. I have never had voltage drop issues with it and everything running. The truck was upgraded to a 93 amp SI type alternator with the later serpentine style belt instead of a v-belt when I did the TPI swap. Before the fans, there were no problems. After the fans, with everything on it went to 12.1v at idle. I had a 125amp SI alternator from a Police car I thought about rebuilding, but have heard they were unreliable at that high an amperage. I looked on Ebay and car-part.com for used and found some 140A CS144s but decided to get a good one and it should last. From my research, I found that Delco rebuilt and Bosch rebuilt seem to have the best reliability. Nobody in my area carries Bosch rebuilt, so I looked on the internet for Bosch rebuilt and the best I could do was over $200 with core and shipping. Advance has a new Autolite for $156, but I was afraid for some reason. Advance has the Delco rebuilt for around $260. Finally, I called the local Delco parts store and bought a Delco rebuilt CS144 140 amp for a '95 Roadmaster for $189 + $22 core + $25 for the 8708 SI-to-CS conversion harness(could have made that, just didn't). I would rather buy locally for roughly the same money as the internet, but there are some savings there if you want them. It came with a pulley with 1 more groove than mine but I just left the extra groove on. On a C3 you would have to swap for a V-groove pulley. The alternator itself is virtually a bolt-for-bolt exact swap. The bottom pad is the same width as the SI. On the top I used a 5/16 bolt and nut so I wouldn't have to ream out the bracket for the larger metric bolt. The adapter plugs right in just as it should. The output lug is considerably larger than stock, so I had to change the terminal on the end of the wire to a larger one. I also added a 2-gauge wire from the alternator to the battery. This step would be different on a C3. On the truck with side-post battery, I just made a ~18" jumper from alternator to the positive post. I have a stud from a car stereo shop that gives me an extra 3/8 post at the positive post on the battery. On a C3, you can go from the alternator to the starter with the heavy wire.

How did it work? I had to go with a 3/8 longer belt than before as the case is a bit larger. On my truck the battery and the plug work out on the passenger side. On a C3, you might want to re-clock the case so the wires came out the drivers side, but there should be enough room to leave it as-is. With everything on at idle it seems to be holding at 14.5v. The voltmeter barely jiggles as you turn things on. I think I could have gone with the smaller version (115amp?) and been OK. I am very inpressed with the idle output with the CS144. Some may say, why not a CS130? Well, I have not been impressed with the reliability of those at all. You can do a CS144 for the same money as a CS130 if you do used, and about $100 more for rebuilt. I am happy Should last a long time.

 

The CS144 is definately the way to go. Much more reliable!
Bernie