I have a C-4 that I have put 2 Altenators and does not seem to charge at idle speed it will go down to 11.2 volts at 650 rpm. If I bring the idle up to 950 rpm it will charge at 12,5+. Driving along it will charge at 13.5 to 13.7 which is good. I have had two times that battery has gone dead but will start with a jump start no problem My question is what do you think I can do to get this car charging at idle.

 

has anyone possible changed your crankshaft pulley maybe changed to a smaller pulley