All I can tell you is that my generator/regulator combo will run at 14 volts in cold weather no load, when the engine/regulator warm up the voltage drops to about 13.5. If I'm driving at 2000 rpm or above, it will handle the heater and lights at 13.0 - 13.5 volts. Delco Remy genny and regulator that were on the truck when I acquired it 8 years ago.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
| 
