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I am rebuilding my 601 with a Viking engine.
I would like to eliminate half the fuel lines in the airplane, namely the return lines to the tanks.
I am thinking about a header tank under the dash or ahead of the firewall.
Anybody done this and how small a tank can I get by with. I will probably have a local fabricator build a tank for me, pressure test it for about 100psi.
Your advice will be appreciated.
I've got a Viking (2013) in my 601 XL. You would not be able to gravity feed a header tank from the mains because they would be too low, so you would have to have an fuel pump to move fuel to the header tank. If you went that route, you would want as big a tank as possible, so you don't have to transfer as often. The returns to the tanks are not that hard to do. I did mine with hard lines on the front of the center box spar ending in bulkhead fittings on the sides of the fuselage, and then connect the wing tanks to the other side of the bulkhead fitting. You can get tapped bulkhead fitting that can be installed in the tanks for the return hook up and use the stock outlets for the feed. You will need to change the fuel switch valve to a 6 way though. I mounted my pumps below the floor in the centerline doubler and made a box cover. This way the pumps stay cool and the only fuel in the cabin is in hard lines.
I guess you could pressure feed the header tank from the fuel pump and then run a pressure line to the regulator/return assembly, and then from the return to the header, but I can see a lot of issues with that (how would you bleed air out of the tank? Pressure in the tank would have to be contolled by the pump, etc) . Viking engines need the fuel pressure to be 39-43 PSI at the injectors.