When I bought my '81' the seller told me I may need a new battery soon. I ran right out and bought an AC Delco battery but didn't put it in right away since the one in there was starting the car just fine One day when I was returning home from a drive the lights were dimming and engine noise was coming through the radio, I also looked and saw my volts were down to around 8v on my gauge . When I got home I replaced the battery and it fired right up, but the voltage gauge was only reading 12 volts . I had the alternator checked and had to have it rebuilt . Once I had it in I took the car for a ride, but a few days later I noticed the gauge was jumping around from 13v-16v specially when I ran the A/C. On the way to the local cruise-in on Saturday I noticed the gauge was at 17v, but when I drove home, it was back at 12v. I asked the guy the first time if he could make it an 80amp instead of the original 70, but he told me this would mean I would have to change other things. I don't have anything that would cause a high voltage pull like an amp for the radio. Would rebuilding the alternator to 80amps do any harm to any other parts of the electrical system, or should I just stay at 70amps? . The guy told me he thinks that when the battery shorted out, the alternator tried to keep up, and burned itself out . Any advice?

 

I have an 80 and recently installed an aftermarket chrome 85 amp alternater. No problems. I can't explain the fluctuations in your rebuilt amp- maybe the job wasn't done correctly.

 

The flux was because something wasn't done right. It might be a bad connection at the BAT terminal on the alternator or the red wire in the connector on the side. Take a look at the connector and make sure the contacts aren't bent or burned. Look at the output connection too, make sure its not melting, if its not connected roght (inside too) it will get hot enough to melt.
CHanging to a higher capacity alternator should not require any other changes. The electrical connections are the same