1989 Chevyrolet K1500, 5.7L. Knocking noise from oil pan. oil pressure 60 psi during cold engine, 40 psi during operationg temp. Tech who listen to engine while running says noise appears to be coming from front of engine. I have replace balancer so far, also noise appears to be reduce when serpentine belt is removed (reduced load). Im thinking front main cap. has any body run into this noise?, thanks.

edit: noise is present only when end of long trip with engine oil nice a warm, idle and trans in park

 

could be a piston skirt broken off, pull a plug out one cylinder at a time,and start it, see if the noise quiets down do all 8 one hole at a time, proly #1 or #2 if it is in front