An oil pick-up isn't going to cure any start-up noises unless it's clogged or cracked, so that leaves You with this;
1)You have excess drain-back, poss. causes are a) filter not equipped or poor quality anti-drain-back valve, b) excess clearances in pump &/or pressure relief valve failing to
close completely, c) overall excess clearances where a heavier "warm" viscosity may help.
2)You have a lifter that has taken to bleeding down on the ramp or nose of the cam lobe & needs a few to pump back up, again a change in viscosity may help.
3)You've got a loose rod that simply will take a moment to shut up, viscosity hail-Mary aside, nothing but new shells is gonna stop that.
