Excessive oil pressure

Taking the S112, BD engine, for test rides, noticed oil pressure gauge reading 70 psi cruising 40-45 mph for around 20 minutes. Idles at 60 psi. I’m using the 1156 cartridge filter. The filter adapter is the type shown in the MT 107. Kevin posted an illustration of it sometime back which I copied and saved. My understanding is the oil pump relief valve should open around 50 psi and the bypass relief valve around 12 or 15 psi. So, 70 seems a little too hot.
Has anybody had these valves go bad or the springs break, or just clog up? Also read somewhere a special tool is needed to remove the valves. Is that the case? Any advice appreciated in advance.

Lets first be sure the right filter adapter is on the block. The filter adapter is determined by the block, not the truck model year. If your block has been swapped, the filter might not be correct.
Check the engine serial number and be sure it is a BD and not a BG.
I don't know when the change was made, from bypass lube to flow and changed where and how the relief valve returns.
Than pull the relief and inspect.
This all assumes that you have checked you readings with another direct reading gauge.

The 1156 is for a full flow filter system, is that what you have?

Regardless of full flow or bypass, no special tools are needed.

Yes, valves can stick, but not that common, however.
If all the above checks out, I would pull the filter adapter off and disassemble on the bench where you could look through the passages and make sure everything is clean.

The 1156 filter is full flow, and the filter adapter has two relief valves which, as I understand it, makes the adapter a full flow adapter. Now CB’s comment as to the correct adapter on that block. It gets fuzzy here. I believe the engine is rebuilt due the engine number having been ground off the boss on the head. It has a lot of parts with a 1960 date code, so I think it’s a later BD. I don’t think it’s a BG, but I can’t say for sure.
It could be the wrong adapter to that block, especially if the valves and springs look and operate the way they should. Taking a look there is the next step knowing special tools are not needed. I’ll post up what I find. Might help someone down the road. Thanks for comments all.

A block for a bypass filter will be supplied oil from the main gallery that runs front to back, and will have one drain back to the sump.
A full flow will be supplied by its own passage and will direct filtered oil into the main gallery after it has been filtered, and will have a 3rd return port for the relief.
Full flow will have 2 valves, a bypass that will open if the filter is clogged, and a relief that will control the max oil pressure to the bearings.

Well, the first rule is do the easiest thing first. (The second rule is a dropped nut or washer will always bounce further than you think). Put a second oil pressure gauge on it and reads 52 psi at idle while the new gauge reads 60 psi. Rev up to 1,200 rpm second gauge reads 52 psi while new gauge jumps to 70 psi. Bad Gauge or sender, I don’t know. New Classic Instrument gauges and very pricey. That’s four out of six that are not right. Thanks to all, a good tutorial for the uninformed.

Glad you got it nailed.
You aren't the 1st to be lead astray by a bad gauge. I have a long story about a neighbor who was lead astray by a bad geiger counter. That led to some fairly nerve wracking hours.

Gauges have all of 30 miles on them. I assumed oil pressure gauge was good. You know the old saying about assuming. I should have paid attention to it. Will I have learned something? Probably not.