The camshaft rotates at half the speed of the crankshaft, so any tappet noise is easy to pick out as the frequency of the tapping sound should be half that of the engine revolutions. The distributor also turns at half the engine speed.
If engine speed equals 3000rpm, then camshaft speed will equal 1500rpm. Therefore tappet sounds will be more distinct.
If you had trouble with the crankshaft, then the noise will be more like a very fast knocking noise or even a growling noise, at it is constant with the engine rpm.