Hard Cranking When Hot

How many and where are your grounds and how big are those cables? 1ga for the positive is pretty big. I would use the same for the main negative going to wherever it grounds off the battery. Then a minimum of 4ga from the engine to the chassis. One to the frame rail, one to the radiator support and one to the firewall. Make sure where the grounds are attached is CLEAN as can be. RIGHT down to bare metal.