VCCA Home Forums Thread Like Summary - Oil Pressure Drops to Zero at Idle When Hot

I have a 1928 Chevy Capitol 1 Ton truck. I have about 1200 miles on a fresh engine overhaul. After I have been on the road on a day like today when it was 94 degrees, I come to a stop light, the oil pressure drops from 8 or 10 pounds to zero. On cooler days I don't notice this. Is this because the oil is so thined due to the heat? Should I run a higher viscisity oil when in hot weather? When I first start the truck in the morning the pressure is 12 pounds. The when it warms up it runs around 8-10 pounds. But as stated, when it get up into the 90's outside, I see the pressure drop and go to zero at idle...?? Thanks, Maxie.

Check to see if the restrictor fitting is attached to the oil filter.It should have a small dia hole in it,as the oil filter is only working on the "bypass" system.You could try disconnecting the oil feed pipe to the filter with a suitable fitting,and if that brings your oil pressure up,you'll have something to investigate.
The other scenario is that the oil pressure relief valve is not seating properly.A mates '28 roadster had a similar problem.Pressure was 6-8 lbs.hot & driving,but barely 0-2 lbs at idle.I ended up stripping the relief valve,re machining the tapered valve seat,and making a new tapered valve head & fitting it to a new stem.After re-assembly of the spring and valve assembly,the pressure is now just over 15 lbs.(cold fast idle),and around the 8-12 lb mark driving.