Rod bearings are a deep noise. Usually they don't make noise sitting and running, but when you throttle it up you will hear it and when you put a load on it you will hear it. It isn't a ticking sound but a real knock.
They usually knock pretty good on start up when there is no oil cushion. They aren't too bad when the engine is good and cold, but when that oil thins it will really knock every time you load the engine up.
It sounds like you haven't really heard it run much, so it could be rod bearings. Try and figure that out as quick as you can, cause if you run it with those bad rod bearings you will likely trash the crankshaft.
Then again, it could be an exhaust manifold leak. That would be easy and cheap!