[Lynn Eades]

I'd like to know the origin of Andrew's By Pass Valve shown in the first photo of this thread.
What is the date on the valve and the makers name please?

I have seen one of those valves here in N.Z. I have heard there is a T16 here, but not seen one. They are at least very thin on the ground here and am now surprised that it might be a T16 part.

Of more importance to Andrew:

These Valves are each used in a different fashion.
The four port valve is plumbed in, in parallel and it is the pressure differential between the "in" and "out" that caused the valve to open and bypass.
Either way FULL pump pressure (all of the oil)returns to the block to run through the galleries, to lube the engine. Just not necessarily running via the cooler.

In Andrew's carrier the oil is directed at the cooler, but depending on the setting of the valve, and the flow restriction of the cooler, a percentage of the volume is dumped directly to the sump. This may be too much.
The bypass spring in the four port valve is a relatively light spring and is not designed to deal with full engine pressure.

I assume yours has a heavier spring fitted.(than the four port valve) What ever this valve opens at, dictates the maximum oil pressure to the engine. It is in effect an external oil pressure relief valve, down stream from the one in the pump.
If your electric gauge is accurate, its max reading will likely be the opening pressure of that valve.

You might like to see my thread on setting the std U.C. (four port) valve.