Ultimate LS and 4 alternators later.
I put the Ultimate LS on a 2003 5.3 Liter Silverado engine into a 64 El Camino. The El Camino with the stock intake runs great with a 2004r overdrive Transmission. I have only 1,000 miles on the setup and have been through 4 alternators. Charging at 14.5 volts for a few months then the alternators just stop charging. The alternator is 105 amps and has electric fuel pump, fuel injection and an electric fan to power it. I had been using the OEM {looks like} 10 gauge charging wire. I called Fitech and they recommended a 2 gauge wire. I made up a 2 gauge wire with soldered ends but I doubt this will correct the issue.
I checked the voltage at four pin plug and the black wire was switched to the ignition and was showing 12.4 volts with a dead alternator. The weird thing was the red wire showed it was a ground but was only allowing 9.4 volts with the other side of the voltmeter connected to the battery. In addition with the engine on when I touched a test light connected on one side to the battery and the other to the red wire terminal the alternator instantly dragged down the idle by a couple hundred RPM and the voltage on the voltmeter went down from 9.4 to 5.
Does anybody have any thoughts on my problem?
You should be using a 140 amp alternator . 105 amps is not enough, which is why they are failing. A auto electric shop could upgrade your alternator to 140 amps. I use a CS130 series alternator in my car which got upgraded to 140 amps. I like those alternators as they have double cooling fans.
Gauge of wire depends on the length of wire between the output port of your alternator and the battery. 10ft is 8 gauge, 15 to 20ft is 4 gauge, 25 ft is 2 gauge.