Let me preface this by apologizing for the dirty engine. This is my daily driver and after 50k, it's starting to look gross. I've never touched it, but looks like I really need to clean it bad.

Let's start with the grounds to the chassis. There are two grounds on my Civic Si that came from the factory. The first connects the radiator crossmember and a stud on the valve cover. The second runs from the chassis to a bracket on the transmission.

Both are made of crappy, small wire that is very stiff. I'd guess both runs to be between 6 and 8 ga. The transmission run is larger then the valve cover one...