Oil Leak, ‘73 2.0 Crate, oil cooler bypass piston? Options

[trick-e]

Car starts and idles as it should. At 10 minutes, it leaks oil. A lot.
Backstory…I’ve had the car for about four years. Ran like a top. Oil PSI has always been high, 65-ish and didn’t change with RPM. Last year I installed the 914werks oil sump extension, and replaced push tube seals and oil cooler seals. Ran it at Grattan in a first timers group. Car ran well all day, then on the last lap the oil PSI dropped to zero. Immediately powered down and called it a day. Couldn’t find any leaks, the oil level was right, and it started and ran as usual, so I chalked it up to a short in the gauge. A couple of weeks later it started leaking oil from around the oil filter/cooler area. Confirmed pressure with a mechanical gauge, still 65 PSI. Since then I’ve been chasing it, and have replaced the oil filter, oil cooler seals, oil cooler, a pressure relief valve (near the oil filter). Could it be leaking from the head or cylinder gaskets? Seems like it would be leaking all of the time then, not just at the ten minute mark. It’s not leaking from the pressure sensor port either. I run 20w-50.

Looking at the diagram, where is the oil cooler bypass piston, internal, in the filter bracket? If valve malfunctions, what happens?

This block does not have the second relief valve.

I’m going to get it up on ramps to get a better look while it’s running, but what do you think?