Grinding, " diesel " noise under valve covers

Another thing, I bought the short block, assembled, for a grand, in 08. Only thing that I didn't build. Other than having the heads checked ( I wrecked 2 rental compressors, ended up buyn a bad *** lever one,, to put my own springs on,, heads were off a running motor, I was told, but wanted em looked at) Trans looked at. The dude I got it from was an Army Aircraft mech, then had his own shop..he was a Mopar racer. Had about 5 340s... and a badass low 10 sec dart.. motor came w/ a soild cam and a spare... I called him, and told him I went to a hydraulic. Drill Sargent mode. Kinda yelled at me..
" YOU DID WHAT TO MY MOTOR!!!! ITS A SMALL BLOCK DAMMIT!" so the clearance thing adds up good..... makes sense