Hello, I have a 2005 2 door blazer and I am about to do a big 3 upgrade with 1/0. I have done this before in a cobalt but it was totally different. I need to know what wires I need to replace or add to. and what grounds. I see the pos going from batt to alt but it goes into a small box behind the headlight before going to alt. I see the ground going from batt to the engine but I don't see one going from the engine to frame or body. Where is this or where is a good spot to add one. I know how the big 3 works just looking for some blazer specific help. Thanks!

Note: I am still running stock alt and batt but am getting a 270 amp alt and d3400 in a few weeks.

 

What people usually do when they do the big 3, is leave their existing wires, and just add the upgraded wire.
The one from the engien to body (from the alt to the body) what I Would do there, and did do) is run the ground to the negative on the battery post. then run a really good solid ground from the battery to the frame.
I hope this clears anything up.

 

So ground from alt bracket to body? (strut tower?) I know theres 2 ground and one power to upgrage, I got the power and from battery to engine but im confused as to what goes to body then to engine? everyone says something different.

Will be running 7-8k eventually so I want it to have strong electrical.

 

engine to chassis/frame, is the alt ground to the body.
so if you have the power from the battery to the alt already done, then the other wire that is there, is the ground for the alt/engine. run that to the - on the battery, or somewhere that will give you a good solid ground.

Now, on my alt when i did the big 3, instead of the ground wire being bolted to the alt, it was a plug, so what I did was bolted the larger gauge wire to the alt bracket, so it was in contact with the alt case.

 

Ok, I may have to just run it from the alt bracket to body as the factory engine ground is buried way down near the bottom almost impossible to get at. So the powers done, then from alt bracket to body and body to battery is that correct? not sure if its supposed to go to fram or just body

 

Correct.
You can run the ground from the alt bracket to the battery negative. then you just have to ground the battery to the body/frame.

 

Ok, do you know where a good spot on the frame would be?

 

anywhere you feel comfortable bolting it to, metal on metal obviously. and as you are already aware of, clean it really well so its down to fresh bare metal.