getting rid of engine noise

when i turn on my nissan pick up, and its running, i can hear a buzzing or engine noise, coming from my speakers. I just installed two amps and about 8 speakers.

you have a ground loop somewhere. You will have to go thru component by component, starting at the amp to figure it out.

I know this sounds silly but its worth a test that doesnt cost anything. get a piece of wire and connect it under one of the bolts on the hood and the other end somewhere close on the body in the engine compartment. This has done the trick on 3 different cars for me in the past. And if it isn't that you wasted a short piece of wire and 10 minutes. Any spare wire will do. Speaker wire even.

that is grounding the hood, I guess it's a good idea if the ground is poor - can help if you are getting pops from the spark plugs