In the Glasair we use a specially machined pair of float valves that
incorporate an overpressure relief valve. They solved our fuel siphoning
problems.

Bruce
www.glasair.org

LancairJim@aol.com wrote:
At the conclusion of my previous posting, I included a PS suggesting
that a
float valve might make more sense than a check valve. In doing so, I
hadn't
considered the thermal expansion issue. On that basis I retract that
suggestion.

Jim McKibbin