Join Date: Dec 2002
Location: Saint Louis, Missouri
I can’t help with factory correct but the best would be to the case of the alternator for charging and to the starter case for starting. The reason for that would be less connections to go through before it got to the negative terminal on the battery (the reverse would be a straight connection from the battery positive to the alternators output post and a straight connection between the battery positive post and the starter motor). Let’s say we move the ground from the case of the alternator to one of it’s mounting bracket. The connection now has to come out of the case of the alternator, make an electrical connection to the bracket and then another connection to the cable end. Most brackets have thin paint on them that is broken through when the mounting bolts are tightened however if the bracket has a thicker layer or harder layer of paint or powder coating on it the mounting bolts may not break through and make a good electrical connection.
The pigtail off of the negative battery terminal goes to the chassis of the car. This can be a fender or radiator support (also take into account or be aware of that sometimes the fenders or radiator support have been painted off of the car and may not make good electrical connections through their mounting bolts when reinstalled back onto the car). If we never upgrade this wire to a larger size or add other cabling between the block and chassis of the car this is the limiting return path back to the battery. The factory only makes this wire large enough to handle what they have designed for the car. If you add a stereo amplifier that requires a 4 gauge to power it then you must add a 4 gauge ground wire between the battery negative terminal and the chassis of the car (providing the amp is grounded to the chassis of the car). There are other ground connections between the engine and the chassis of the car and these include the emergency brake cables and shifter cable. If the main ground on the block or the pigtail starts to become a restriction then those cables can become welded together from them trying to pass the current through them.
When I do battery connections I clean the area where the wire terminal end will be attached at and then use a star washers between the terminal end and the mounting surface and tighten the bolt securely. If it is in an area exposed to moisture and water, I cover the connection with silicone to slow down the corrosion process. On my mid 70’s Chevrolets I have always used the hole on the top alternator bracket and not had a problem and had the pigtail on the inner side of the fender.
On customer's cars where I've installed a high output alternator there is a threaded hole in them for easy attachement of a ground cable that then goes to the battery's negative terminal. If it's there, use it.
1974 Spirit Of America Nova (being restored), 1973 Nova Custom, 1968 Chevy II (Garage Find 2012)
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