Bill,
# So pressure relief for the sump has to
come thru the lines from the wing tanks?
The vent & check-valve setup on the sump allows the sump to “burp” thus allowing you to have a full sump on each side.
Any actual venting occurs through the wing tank.
Also not shown is an additional check vale that allows cabin air to be used to break a vacuum in the system should the outside vent ever become obstructed by ice, insects, etc.
# This doesn’t sound like a rotary,
what are you installing?
This is a Lycoming IO-360 installation on the Velocity. I picked this up last March and plan to fly it until my Long-EZ R/G is completed.
My Long-EZ has a rotary with a very similar fuel system. The only difference is the mechanical fuel pump is replaced with a second electric fuel pump.
T Mann