Therob- What are your thoughts on how low the second tank will hang? For the street it doesn't matter but if you are looking at keeping it on permanantly then it may be an issue for some depending how they drive offroad. Beach drivers it won't matter but rock guys that claim to constantly bounce of rock shelves onto their bumpers may be in trouble.

Also for the plumbing I think if you vent the aux tank into the same vent tube as the primary you should be ok. Also if the tanks are at the same height then you can get away w/ a passive system by just running 1/2" hose from one to the other. Make it so that it is on the lowest side/point of the primary tank. This way you empy the aux before the primary. Your fuel gauge will still be accurate because it will pick up from it's normal spot and read correctly - it'll just take long to read "E"....

the other way is to have a 12v "Holley" style pump mounted to the aux tank on a switch , this way when you reach "E" on the main you can turn the pump on for a minute and "refill" the main tank.

Vent heights and tank heights are very important if you are going to fill both tanks from the stock filler neck. If this is not watched carefully you will be pushing fuel out the vents while trying to fill the higher of the 2 tanks.

If you are going to fill the aux tank from it's own filler neck then the issue is there based on vent heights and pressure of system (again not an issue if a pump is used because it acts as a gate ) but not as critical....

*** any engineers that want to jump in here and give feedback I welcome it ***

Another option (although slightly scary) is to use a marine square tank in the cargo area wired to a 12v fuel pump. The out let line goes through the floor and "T's" into the filler neck of the main tank or directly into it.. Same thing , when you get to "E" you flip the switch and refill your main tank. This set up is what you typically see (sort of) in street/race cars where there is a fuel square tank in the trunk that is run to a pump and braided line to the fuel rails or carbs...

You can get a really good fuel cell and pump for about $200...then it's just labor hours.

just my .02 - I'm sure everyone will flame for this, but will beg for directions and pics once it's done.



this might not be an issue to most but for the long road trips I take (3000-5000 miles each) if I can get an extra 150 miles before I have to stop it helps...