I am a teenager who is building an engine for a 87 Nissan 300zx and i am trying to decide between a Carburetor or fuel injection. I want the most speed i can get out of this engine what should i do?

if you are rebuilding a Nissan 300zx motor VG30E or VG30ET then obviously you will go with injected because the ECM (computer) is already setup for top mounted injectors.

Whereas if you decided to go with something a little more creative like a small block V8 I would personally do a carb, but either is appropriate for you application. It just depends on how mechanically inclined you are... I have 5 muscle cars and absolutely love carbed motors. Really easy to work with, very simple and dependible.

My 300zx is my competition drift car and accepted the fact that its injected and just worked with it.

Also, if you are rebuilding a 300zx engine (or any motor for that matter), spend the extra 80$ or whatever and get a new timing belt kit. The VG30E(T) motors are interference motors and if you want power to play with the last thing you need is to have that break and crush your top end.

hope this helps