Hey guys I got a 1990 caprice wagon with the olds 307 motor. I sometimes I hear a tapping/knocking sound. It’s very intermittent. Usually hear it mostly around idle speed, goes away when the revs get higher and sometimes doesn’t make the noise at all.

it seems to only make the noise when the engine shakes/runs slightly rough

I tried to get it on video, here’s a link https://youtu.be/BB9OK-S5djk

Any ideas what it is?

 

Anyone?

 

Could be a sticky lifter if it's a "light weight" sound. A heavy hollow
knocking might be low oil pressure at idle, letting the journals rattle
(mains or rods) when it runs rough. Might play with various oil weights
and see if one (likely higher viscosity) helps out. Engines with a lot
of wear, tend to lose low-RPM oil pressure to the weeps.