Where to drain gas tank behind seat 70 f100 sport custom

[390BigBlock]

I haven't started my truck in a couple years and I want to drain all the varnish outta my gas tank before I start it back up, I went directly underneath the gas tank (underneath the truck) and I saw a rubber hose connected to 2 steel pipes I slipped one part of the hose off n really no gas was leaking out, I poured a half gallon of gas n some sea foam into the tank also. I just wanna make sure I'm at the right place or if there is something wrong. Can someone help me out??

[Ranchero50]

There isn't a drain. You have to remove the tank, flip it upside down and shake it to get the fuel to come out of the fill tube. Not really worth it to me, just fill it up with fresh stuff and run it out a couple times.

I haven't put gas in my '68 Fairlane since '08 and it starts fine.

[390BigBlock]

I have a inline fuel filter that is about 6 inches before my carburetor, disconnect the fuel filter and go turn the ignition on n physically pump the gas petal into a small bucket, would I flush most of the gas out of the tank? Or.....

[sargentrs]

I siphoned out most of mine through the filler neck the old school way (don't swallow!). Then disconnect the line at the fuel pump, remove the coil wire, and crank the engine to remove the last half gallon or so.

[Ranchero50]

Nope, if the engine is stock it has a mechanical pump so the engine needs to turn over to pump the fuel.

You'd have to rig an electric inline pump up to draw the fuel out.

Really, filling the tank with fresh gas is about the only way to get any varnish to dissolve.

[sargentrs]

Really? So the engine has to be drawing a vacuum in order for a mechanical fuel pump to push fuel up to the Carb? I did not realize that. Never actually done what I suggested. I pulled my tank and poured the last of it out. Never too old to learn! Thanks for that insight Jamie!