engine tapping

I have a 1995 J30 which has begin a pretty loud engine tapping on the left side. It seems to tap as fast as the rpms. The engine is running fine otherwise. any ideas?

It is most likely the idler pulley on the timing, these cars naturaly sound like sewing mechines, but if that gets really loud replace the pulley professionally, I replaced my motor for $2500 because I did not have that pully changed.That motor is an interferance motor just turning it over with the starter will bend the valves if the timming is off at all.

Check The other thread about engine tapping