[wslade2]

while working on CiES probes I replaced o-rings at the close off balls in my other valve. They were definitely on their way out once removed and inspected. (on the other valve one had totally disintegrated and disappeared.)

O-ring size confirmed: 5/16 " ID x 7/16" OD x 1/16" cross section (CS)
Again, this is where the ball will press against the valve cavity port/o-ring to provide positive shut off. I used fuel resistant o-rings.

If you use a right angle pick and firmly pull, you can pull out the main retaining ring without damage for reuse. Might have to grind pick end short to fit. I pull it out while holding it down in a 5 gallon bucket so that when it "pops" the spring and ball don't go flying. It'll be a pretty strong tug. There will be another smaller retaining ring holding the o-ring in place. Retaining rings can be pushed in with screw driver and positioned. For the main ring, which can be stubborn, once past the first few threads can use an AN fitting to "press" it all the way down.

Used fuel resistant gasket material from auto part store to make valve body gaskets by tracing valve and old gasket. $9 leather punch from harbor freight to punch out screw holes. The material I got was thin so had to double it to get right thickness. First inspected valve operation visually after reassembly and then tested valve by blowing air through it before putting it back in.