When my hood is closed, my V8 sounds really quiet... However, if I open the hood with the engine running, I hear some VERY loud ticking... I ended up tracking it down by listening and it's actually just the fuel injector pintles opening and closing. I thought something was wrong with mine the first time I heard the engine idling with the hood up, but it's nothing.... If you close the hood, it is barely audible on my 4Runner.
Ricky