running second power wire, grounding amps

i have two questions

first: i am running a second power wire(8 guage) in addition to an exsisting one(10 guage) would i just be able to put the larger wire underneath the smaller one on the battery post? or would i have to get a special battery terminal?

second: for grounding amplifiers is there a certain type of screw or nut i should use? and whats the best way to go about it?

Make it easier and run a single 4ga. then split it to your smaller wires with a distribution block. for the ground make sure you scrape away all paint/coating and keep it as short as possible. grab a self tapping screw from your local hardware store which probably sells them individually.

but would i be able to run them with the larger one below the smaller one on the battery post? i already have the two power wires so if possible this is the way i would like to do it

If you are asking the question, I would have to guess that you have a General Motors product with a side post battery.  They do sell a new bolt for this purpose.  It has a bolt that replaces your original that has a threaded nipple on the back side with a nut that tightens and easily secures up to 5 or so ring terminals.  Go to your local stereo shop and ask them for a GM battery post extension.

Yes you can run both...Yes you can just connect it to the battery ensuring a tight connection(although an aftermarket terminal would probably apply here...) If it is a side post...Mr. Iamanidiot explained it well...! BTW what is the 10g for...Here is some infi from BCAE1.com...Also these TWO wires are FUSED at the battery?

1. Installing Multiple Amplifiers
   Main Power:
   When installing multiple amplifiers, you have a few options. If you already have a moderately large wire (8 gauge) for your first amp, you can run a second (appropriately sized) fused wire for the second amp. If you don't plan to add any more amplifiers in the future, this will work fine. This will not require that you buy a distribution block. The second solution would be to install a large wire (suitable to supply both/all amplifiers). A 4 gauge wire is the most common size wire for the main power wire. For a 4g wire, you can use a main power fuse as large as 150 amps. I don't recommend anything larger. The main power wire would run through the vehicle as before but when it gets to the back of the vehicle, it will be connected to a distribution block. The main power wire would go in the larger connector and the smaller connectors would go to the amplifiers.
   Grounding:
   It is OK to ground all of the amplifiers in the same place (if the ground wire doesn't need to be extended to more than about 18 inches). If the amplifiers are mounted on opposite sides of the trunk, I'd probably use 2 ground connections (with 3/8 bolts to the vehicle's floor pan).
5. When making the ground connection for the amplifier, the floor pan of the vehicle is a better choice than some of the braces and other metal structures that you may want to use for ground. Braces and other such structures are sometimes connected to the vehicle's chassis (body) by a few spot welds which will provide a less than optimum ground return path.
6. If the amplifier's ground is properly connected to the body of the vehicle, it will provide a better return path to the charging system's ground than will a ground wire run back to the battery. This is especially true if the ground strap from the engine block to the chassis is upgraded.

TECH TIP:

For a good ground:

Get a 3/8 inch bolt, nut and lock washer, find a place on the body that can be accessed from the inside of the vehicle and out. You must be able to get to both sides so that you can hold the nut from turning when tightening it up. Drill a 3/8" hole for the bolt, making sure NOT to drill through any fuel lines, brake lines, the gas tank or anything else. Scrape the area under the bolt (inside the vehicle) to remove ALL paint and primer then bolt the ground wire's ring terminal down with the 3/8 inch bolt.

As a side note:

For grounding devices that draw only a few amps (like crossovers, head units and equalizers), you can use virtually any type of screw. Many people warn against using the black oxide coated screws but it won't make a big difference because the electrical connection is between the ring terminal and the metal surface that's been sanded clean and not through the screw. The screw simply holds the ring terminal to the metal.

-------------
M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

wow awsome! thanks alot guys!

You should also use some dielectric grease on all your exterior connections. Anything under the hood or exposed to the elements. I recently took apart some power wires most were greased and they were spotless, the wire and the mating surfaces. But the one's I had forgotten had gotten corroded. So to keep good clean connections, use the grease. It's available in any auto parts store.