I was trying to refrain from comments.. as they seem to be too technical for some folks.. but I have to comment.
Using an "air" valve, as noted, for gasoline, is pretty ... well, I'm not gonna say the multi-word.
to condone, or even suggest it, or accept it, is totally irresponsible. If someone wants a fuel shutoff, find one rated for FUEL...
that in essence, combined by the flow and thermal attributes of the valve noted, just places people into the "Darwin zone".
suggesting this, to a forum of people that don't get/may not be, really technical, places the burden of shame, on the person posting.
BTW, a bunch of this is old school, many times discussed,(we have discussed, and examined all the "cheap" fuel valves, and found actual passage port sizes in the 1/8", to .140" diameters), and found to be not really viable for use.. the actual "flow" orifice, within the valves suitable for fuel, are way too small (don't confuse the NPT fitting size of 1/4", with the actual port thru the valve body, which is greatly diminished)..
If you doubt this, call Murph... when this first popped up, he did find a suitable valve, but in later discovery,(after some of us tested flow characteristics, ) decided the flow was "not reliable", and dropped it.. some of us have been here a long time, trying solutions. Best solution is a good petcock build, and associated overflow tubes as a backup.
nuff said.