Oil light stays on too long on a cold start

Killer6 said
The slanty I built had a lot of oil press cold with 10w-40 in it, like 90-95psi cold, it would idle hot at 20-25psi & peak close to 70psi wound up. No idea to this day why

Because 10W40 is WAY too heavy an oil to be running in a newly-built (or oldly-built but healthy and sound) engine.