Let me throw my in here about size and application on wire sizes in D.C circuits, to little of a wire will increase the resistance during large current requirements (starting the motor), it forces more current through the smaller cable causing heat in the wires which increases the resistance To large of a cable size is not usually a problem in cars, especially race cars Proper grounding is As already said use two grounds in the back and the same size cable (# 1,0 or 00, not #4 or #2 ) as the hot feed for the ground to the front and attach it to the motor with a large wire size eyelet, I use a 7/16 eyelet soddiered(SP?) onto my cables and attach them to the 7/16 transmission bolts to the block for the ground and directly to the starter lug on the starter for the main feed from the batterys. I use a #2 cable for the main feed to the rest of the circuits on the car from the starter One of the things I have learned on low voltage circuits is to use the largest wire size needed to avoid any voltage drop at the far end being tested You will always see a voltage drop at the starter motor when it is spinning the motor over, you shouldn't see any voltage drop at the starter when it is not being used (or anything else drawing curent)versus checking the voltage at the batteries BTW, on digital VOM meters don't worry about a change of .01 volt differences, do worry if it is more than that there shuold be very minimal voltage drop, less than .01 volts, through the main battery feed to the front