Thanks everybody for their input. This is why I love the Rotary Forum.
 There
 are so many different guys with a wide variety of expertise, that there
 will
 always be someone with firsthand practical experience to give their
 opinion.
 Because I don't fly that often, I tend to think what works well for a car
 will automaticaly work on an aircraft.

 Attached is try nr two. I want to have a system that is simple,
 inexpensive
 and requires minimum input from the pilot.

 This is essentially an electrical controlled system (In my trade). I'm
 thinking of having a centre console mounted rotary switch with left, right
 and off positions. In the left and right positions it will switch on the
 relevant Facet pump and open the relevant return line solenoid. A
 mechanical
 overide will be incorporated to prevent me from switching it Off by
 accident. My thinking on the centre solenoid, forward of the HP pumps, is
 to
 have it open for both left and right positions but closed in the Off
 position. This is to cut off all fuel in case of an engine fire.

 The left and right HP pumps will be controlled by two switches on the
 panel
 so that either one or both can be switched on as required.

 I'm planning to build an electronic timer to give me a visual
 indication,flashing LED, of approx. 20 minutes to remind me to switch
 between tanks.

 I have a few qustions though:

 1. Will the HP pump ensure that the facet pump does not pump fuel
 overboard
 through the vents. I'm thinking to maybe wire it up in such a way that the
 Hp pump is switched on before the Facet pump goes on. Or would I need a
 mechanical way, needle and seat or float valve to control it?

 2. Can I use car airconditioning solenoids for the fuel?

 3. Are there any restrictions on the size of the surge tank? Can I use it
 to
 increase fuel tank capacity?

 4. Are the fuel supply and return lines the right size?

 Pierre


 I think you should return all fuel to the sump tank. No return solenoids
 required.
 A float valve is a good idea. The facet pumps are used to feed carbs with
 float valves. T the Facet pumps together before feeding the sump. Check
 them
 for one way valves. If they don't have them get some.

 Here is your 2nd drawing modified to my suggestions.

 Questions:

 2. I don't know.

 3. Other than weight and balance no. Yes it can be used to increase fuel
    capacity.

 4. 3/8th are fine for everything. Vents can be 1/4 inch.

 A sight gage on the sump tank is a good idea if it is mounted high.

 Paul Lamar


After a while with out the HP pumps going
the facets would pump fuel up through
the vents in system 2. Why I like Pauls drawing 3.
Simpler too. Non return valves after the facet and
the float valve, I would say in the surge tank, will be
necessary to allow room for returning fuel. And
stop one facet from losing fuel flow into the
opposite tank.

Not sure what facet pumps you are using, but the
facet pumps used in earlier Mazda vehicles were
only good enough to supply a standard 12a or 13b.
Any mods to those engines and they would prove
to be inadequate. Why I liked the Holley LP pumps,
they had much better flow volumes. A Holley blue
would easily supply my old 12aT at 250hp up
to 305hp.

Sam