[olddog]

I have a 347. I purchased a running car, so I cannot say what starter is on it. It is a smaller starter than factory. I assume it is a mini high torque of some type. It has never failed me. On a hot day when I get gas, I can tell it turns a bit slower, but it always starts just fine.

If you are certain that the wire size is adequate (both positive and the ground), and the battery is not the problem, then I would look at a different starter. My car has the battery in the trunk and a short wire grounded to the frame. Then a ground wire went from the frame to the engine. My starter turned slow and the voltage meter dropped to 9.5 volts when cranking. I really didn't like putting 500 amps through the frame. I added a heavy ground wire, from where the battery attached to the frame, to a bell housing bolt near the starter. The starter turns faster and the volt meter only drops to 10.5 now.