If I can get a definitive reason not to set it up like this I will move on to a dual filter dedicated to the engine fuel line.
You would need two Y valves plus hose and clamps to make your plan work. You can't get by with T junctions. You make each Y valve accept from either racor yet supply only one engine. That is why you need two Y valves. The return lines from the two would of course remain as they are since you only have one tank. You never
try to a operate a two from one racor setup even if only one is operating.
In the above setup the idea is you leave things as they are now with the valves set as they feed now. Should the emergency
come up that you need the crossover to draw from the other racor you could for either engine doing a double valve switch. Set them up so they point the same and always know they both need to be the same and you are fine. You have two valves with two positions each. 2 of the permutations work the other two are disasters. You have 50 /50 chance of shooting yourself in the foot with the weapon you are about to install. It should be really really obvious how they go.
You want to locate all this plumbing
as close to the racors as possible using the least amount of fuel
line as possible. Don't just let the valves hang loose! You need to mount all this to an epoxy
treated piece of plywood
all nice and pretty with big bold first mate proof lettering. It should be some place you don't have to stand on your head
to get at and should be well lighted (or add lights). You want no fuel lines running loose. They should all be firmly attached to bulkheads so they can't flop around or be knocked loose by falling objects or a loose foot attached to a crew member
Spend the money
and get the really good valves. If you don't, the valves will leak air down the road (may anyway). It shows up as not expected and takes a long time to figure it out. You will by then have forgotten this posting
. My setup is two racors with two tanks
and now 18 years later I'm chasing air leaks
. Mine wa installed quite well by the PO. It isn't the easiest place to get to but it is lit well and poorly labeled. Lots of hose clamps (use only 316 clamps).
Make sure you bleed the system for both lines at the same time so you can easily do this instant switch and not have to rebleed the line. Testing just sounds too easy when you switch out the filters normally. If you don't do that then the whole system really is not useful. It means swap both filters at the same time need it or not
. The warm feeling knowing you did run both engines and did a switch over test makes you glad you did all this work. It's not a cheap
or that simple a thing to install well.