Thanks for the info. Oddly, I don’t have permission to view the forum link you sent. The 50 psi target number for dumping oil is the number I sought.

The spring was not really rusted when I pulled it out. It was somewhat dirty, but not too bad. I manually pulled the compressed section apart to stretch it back out. It generally seems in ok shape. It doesn’t seem to have any weaknesses. However, given I have the valve apart, I’m going to try to find a replacement spring.

I will definitely be doing some math and experimentation to figure out the right configuration, erring on the side of having slightly lower than desired pressure initially and working my way up to the desired pressure.

A friend is fabricating a new tube from steel. The tube should be ready this weekend. I drilled and tapped the nut already for the tension adjustment. Just seeking a replacement spring at this point.