I have a 68 c20 with as best as I can tell is a 76 350. Compression is good in all cyclinders from 170-180. after the engine warms up I can hear a knocking sound, actually more like a hollow tinging sound, kinda hard to describe that increases when you up the rpms. Using a stethoscope it seems loudest at the water pump but not the block itself, but the noise is still there when I disconnect the fan belt?? anybody got any ideas?

Thanks,

Milo