You might be better off replacing the small factory tank with a larger one, to keep all the weight as low as possible.
I thought that it was Federal laws that prevented gravity flow systems. Something about some vehicles leaking fuel after a collision that caught fire, and all that. Our Government wants us to stay alive, so we can keep paying taxes. . .
Really, new regulations from the EPA say that a fueling system can not evaporate more than a few grams of fuel each 24 hours. While before 2004, a Ford truck could allow up to 30 grams of fuel evaporation per 24 hours, after 2005 the limit was much stricter 10 grams per day. You can thank an environmentalist that your car is now safer, and will not vent fuel into your garage at night. Sure the car will cost $800 more, but it is safer! And will not leak out 10 ounces of fuel vapor per month in the summer time anymore. .
So do you have the weight capacity to carry a second 50 pound fuel tank with another 300 - 400 pounds of fuel in it? If you had a gas truck the engine is lighter, and you might get away with it.
Fred.
