There is a military aviation valve that is a match for the Stearman fuel valve in functionality, mounting, and size. It is a bit smaller than the original D-3 valve.
This is a ball valve with the 1/2 inch flare fitting on the top with the threads for a bulkhead nut to attach to a bracket and a 1/2 inch slip tube fitting on the bottom. These are the same as the original valve.
The clocking of a 90 degree CCW turn from “OFF” to “ON” is the same as the original valve.
This aviation valve was made by Koehler of Dayton in the 60s and has P/N 07901-3.
I, and many other Stearman owners, have been using this valve for many years and have never heard of one leaking. When restoring the Greek Stearman, I had a new D-3 original valve, but chose to use one of these Koehler valves instead due to its unobtrusive mounting and long term reliability.
This installation requires a coupler that fits over the winged control on the valve, and then is taper-pinned to the control tube leading back to the fuel control handle in the front cockpit.
The mounting bracket can be made out of 2 inch by 3 inch aluminum angle as shown on the left in the picture, or as a welded up unit with side braces as shown on the right. Either works just fine.
The bracket mounts on the diagonal tube just aft of the firewall, just like the original valve. It uses two opposing tube clamps for mounting. This mounting positions the valve in line with the control tube.
This valve was originally used as a fuel drain valve, and as such, was spring loaded to the “OFF:” position. When I first utilized this valve, I removed the pin that holds the control the wing. This allowed removal of the small coil spring for “OFF” position loading. Then I replaced the wing and then the pin.
A much simpler method is as follows: When facing the control wing on the valve, there is a small slot at 45 degrees to the control shaft. This slot holds the end of the coil spring that loads the valve to the OFF position. By holding the control wing at 45 degrees to the valve, one can then slip a thin Dremel cut-off tool down into the gap and cut the end of the spring that fits into the slot.
The valve then has no spring loading in either direction, but has positive detents at both the open and closed positions. An added advantage is that you can feel the detent when operating the fuel control handle. Getting a 337 for this valve was pretty straight forward.