Doug my engine machinist forbid me to fill my 512 block even tho it was for strip only, told me the wall thickness is plenty suffiecent and that filling will change the temp at the lower end of the bore to cause piston scuffing and different wear charistics, now that said I did a half fill on my strip only 408 small block and have noticed that the oil pressure would drop quite a bit the more I ran it and had me concerned during round robin passes at the end of the class run's, is it because of the excess temp in the oil? don't know but that would make sense to me,,oh and by the way I ran Brad Penn 20W50 semi synthetic, proof will be in the teardown and freshen-up.