I made the rest of the valve parts today.... Here is the finished poppet and stem seal....



The poppet is made from 3/8" diameter PEEK, and I threaded the end of the 1/8" drill rod stem to 5-40 thread, drilled the PEEK with a #38 drill (tap size for 5-40) and counterbored it 0.10" to 1/8" and then just wound the stem into the PEEK, letting it cut its own threads until it stopped.... It was so solid I couldn't back it out.... I then cut the head to length and turned it for the spring seat right on the stem.... It sealed first time.... The stem seal is a #006 70D O-ring sitting in a 1/4" diameter recess in the valve body, held in place with a short piece of 7/16" bolt faced off flat on both ends and a screwdriver slot ground in the end for installation.... It has only enough drag to barely hold the weight of the valve body, so considering the forces on this valve shouldn't even be noticed.... The inside of this valve is huge....



The throat (visible in the bottom of the rear section on the left) is 5/16" ID, so the seat margin is only 0.030".... The valve is drilled 11/16" ID, leaving a 5/32" gap all the way around the poppet head (4 times the throat area).... The front of the valve is drilled 13/32", the same as the front ID of the conical valve spring, and so has twice the area of the throat, allowing the air to enter the valve from the reservoir much easier than it can get out.... I don't think there should be any problem with this valve flowing air....

Bob