Grinding, " diesel " noise under valve covers

i had a "diesel" type noise in my LA Stroker. it didnt just show up one day. it was always there but it got loud enough to notice. could never figure out what it was . long story short i had to dismantle the engine . i found that the cam bearings were wiped out. this was originally a blueprint engine with low miles. cam bearings were bad enough that the chain was loose. when i replace d the cam bearings i never heard that noise again. ??????