from what an electrician (who quit and opened his own car audio shop) told me, that would defeat the purpose. Think of it like this: You have a box. Coming INTO the box, you have a water hose that for this example, puts a gallon every 10 seconds into the box. Going OUT of this box, you have a 4 inch pipe cable of pulling a gallon a second out of the box. Do you think that with a water hose going in and 4 inch pipe going out that you're going to be able to pull a gallon a second out of that box? Of course not. you can only pull what's being put in. LIKEWISE, you can only pull the current from a battery that you have going into it. If your battery is grounded to chassis/frame with zero gauge wire and you run another zero gauge wire from engine to Neg. battery terminal, you're defeating the purpose of running that wire off the engine because you're only going to be able to pull a 0 gauge's worth of current in stead of two 0 gauges worth. As someone has stated on here, electricity running DC runs from ground to positive. So the more ground you have, the better so by grounding the engine out to the chassis and the battery to the chassis, you are giving them both their own bit of current.
Now before someone jumps on me and says i'm retarded, simply think about what I said. It makes perfect sense to me and if you can think critically and know an electrician, it should make sense to you too. That's my two cents //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif