[DrDave]

The oil pressure lines from the motors are copper lines. They are prone to cracking. Over the years they lose their ductility. There are no unions in those lines until they meet up with the barely flexible lines at the inside of the front firewall behind the gauges.

A good test is to pull the line from the rear motor at the T on the passenger side in the middle of the case. Pressurize that with your nitrogen tank to no more than 50psi. You can T in a tire pressure gauge to that test line too. This will facilitate finding a leak and give you an idea of the accuracy of your oil pressure gauge.

In performing this test to repair a leaking oil pressure line in the belly I found that the response of the oil pressure gauge is poor. Below 30psi the needle didn't move. At 50psi it slowly came up. I flushed out the line with solvent but it made no difference.

Dave