i have a newly built 350, the oil pressure is fine when cold or with high rpms, but when its hot and idleing its under 10 psi, i just had the crank ground, it has new bearings, mains and rods, i changed oil pumps today, will finish tomarrow(high volume/high pressure pump) the old pump was 1 year old, the heads, were supposedly newly machined, has a new lifters and cam, i never had the rods checked for round, oh and i have a manual gauge on it, if the pump doesnt work what else could it be? thanks for the help

 

You might have an oil gallery plug missing. They remove them to clean oil passages and sometimes forget to put them back.