Club Cobra - How were the gas tanks with a reserve set up?

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How were the gas tanks with a reserve set up?

I have a custom built gas tank in my car. I just found out (DUH on me...) that it is set up with a reserve type feature, having one fuel pickup closer to the floor of the tank than another, so that when the main supply runs out I can switch to the reserve pickup and use the remaining small quantity of fuel to hopefully get to a gas station. I have two setup choices. One is to use only the "reserve" pickup so that my tank can be used until dry. The other is to use the two pickups with the lower one acting as a reserve. I suppose I'll need a valve of some sort and perhaps two pumps to do that? Can anyone fill me in on how this originally worked, and maybe what type valve and would be needed and where you guys using this setup have the valve located?

Doug

Contact John Bessey, he has valves.
jkb5 at sbcglobal.net

Think original 427 used two pumps, thus one for bulk of use and one for reserve.

I do not have a gas gauge as I was replicating a comp car. My higher pickup is connected to my mechanical fuel pump and is used 99% of the time. My lower pickup is connected to my electric fuel pumps in case I run dry or need more fuel pressure / volume. They come together in a tee just before my fuel filter and fuel log. I believe this is the same setup as the original comp cars with the SW240A fuel pumps in the trunk.

My first suggestion would be replace the Tee with a "Y" AN fitting to reduce a pressure losing restriction. I would attach my one way valves to the Y. Second, you need TWO one way valves, one for each line. Back in the day electric fuel pumps had one job, move fuel from the tank to the mechanical pump PERIOD. I believe with your present setup, if you were racing you would quickly run out of fuel being delivered to the mechanical. I would look at the following: Connect ONE pump to the reserve, connect the second pump to the higher pickup, wire this so the second pump it is HOT when you turn the ignition on. Your present setup will over power the gravity feed line and pump fuel to the higher pickup, pumping fuel from the reserve reservoir into the main tank. The Daytona's had a 3 pump system because the electric pumps of more than 50 years ago were not very reliable.

Bill K

The 427 comp cars used two Stewart Warner fuel pumps on one on-off toggle switch, they were mounted so that both were fed by the same port on the fuel tank for the reserve side and ultimately fed the mechanical fuel pump as a booster system only. The problem with this setup was that if one of the pumps shorted and blew the fuse both pumps stopped working. Once fuel pressure was present on the fuel pressure gauge the electric pumps were shut off and the mechanical pump drew fuel through them. The primary fuel line went directly to the mechanical pump. You would need a one way check valve on the reserve side to keep fuel going in the correct direction when using the primary feed.
If you are not using a mechanical pump, you can use two electric pumps on a on-off-on toggle switch to supply fuel to a “Y” connection but you will need two separate check valves so that the fuel does not back feed to the tank from either circuit. I’ll see if I can find photos of a dual electric pump, dual check valve system I did on a 4000 Series a little while ago. I also incorporated a electric fuel pressure sending unit that worked with an electric fuel pressure gauge.

Thanks to you all, I appreciate the input. Much easier to understand now.