That is small but very crucial detail that you should have mentioned in your first post. Where you measure pressure in a hydraulic system matters a lot and it did not occur to me that your pressure gauge was not connected to the normal pressure tap between the pump and the relief valve. It's as if you're concerned about the water pressure in your house but you've put your pressure gauge at the end of a garden hose.
A positive displacement pump (ie, your oil pump) generates a flow rate that is directly proportional to oil pump speed. The pressure measured at the outlet of the pump is actually measuring the oil's flow resistance downstream of the pump. If you were to hook up your pressure gauge to its normal location (where the oil pressure switch is located), you will see a much higher pressure at idle. See Engine Wear.
If you're still using your oil pressure switch, add a tee to pressure port and move your oil pressure gauge to it. With a high volume oil pump, my guess is that your oil pressure will be constant at all times because it will most likely be always at the relief valve pressure setting and oil will be constantly relieving back to the sump. I would try a lower viscosity oil like a 10W-30 API CK-4 HDEO (with a Ford WSS-M2C171-F1 approval), which will get more oil to the bearings and less to the sump. I like PetroCanada Duron SHP 10W-30.
You sound like u never messed with a big block Chrysler. I have 2 mech oil pressure gauges on mine , one in the cockpit, one on the firewall, both come off at the stock location in the rear top of the block, both read the same thing, even tho they are on opposing ports, one is 1/8" pipe and the other is 1/4" pipe bushed to 1/8" for the oil fittings, which are at the end of the line in the oil system------------
NO FORD STUFF ON MINE !!`
