I had battery next to the engine and used 4ga. With stock LS7 it would often not crank on first attempt. Upgraded to 2/0 wire and it would zing the motor over every time. 2/0 is overkill. But you probably need 2ga at least. If the run battery to starter is over 6 feet, go to 1/0.
if the run goes through a switch, try bypassing the switch and see what it does.
You can test all this with a GOOD set of jumper cables. Leaving all else hooked up, put cables on the battery. Other end, ground to a starter bolt, positive to the starter hit stud. If that “fixes” your issue it’s either ground or supply issue.
if the run goes through a switch, try bypassing the switch and see what it does.
You can test all this with a GOOD set of jumper cables. Leaving all else hooked up, put cables on the battery. Other end, ground to a starter bolt, positive to the starter hit stud. If that “fixes” your issue it’s either ground or supply issue.