I just got a 4 gauge amp kit that i'm gonna use with a distro block to get 2 8 guage. Do i have to ground the battery? I thought i just have to run the red power back to the distro block and just ground the amp. thanks

 

The battery is already grounded. Just ground the amps and you'll be fine.
Kevin.

 

yep, what lunchbox said, and remember to scrape/sand off the paint on the body so that it'll make a good connection to the frame of the car when you ground the amps.

 

Ditto what everyone else said. Make sure the ground and power cables are the same guage. The ground wires should be as short as possible and ground both amps to the same point.

Tony