clickity clack

What does it do above 2700? Below? Do a compression check first to get some idea of the condition, if this checks out good, then check for other problems. If the compression is bad, you might as well look for something soon to replace it with. RPM related noises that are specific to only certain rpm's are sometimes hard to figure out because you are driiving while it is happening. Things that come to mind: harmonic dampner, valve springs or even heat riser valves can make noise in a narrow band of rpm. Usually things like rod bearings or mains or rockers will make noise at all rpms if they are bad.