FI bus tank question

[babysnakes]

Why do the late FI bus tanks have the return on the bottom? I want to put a Suby in a '69 bus using a '72 tank. Can I use one of the 1/4"+/- vents on either side up top for a return? The center 1/2" is the vent for the tank that exits at the fuel filler.

[Jadewombat]

You could. I used my fill hose for a while because it was easier to tap this for a fitting.

[babysnakes]

After digging deeper into this forum, it seems to be a bad idea to return the fuel from the top. It creates bubbles and other interference. Looks like I'll be putting the return on the filler neck.

[skills@eurocarsplus]

you have it backwards. ok to return from the top, not from the bottom. the big issues with a bottom return is getting bubbles that may get sucked back out by the fuel pump, causing vapor lock or a host of other weird issues.

can you run a T on your stock outlet? sure can. some do without issues, but it is pretty ez to just dump it back in to the top of the tank

[fl_buggy]

If you look in a FI bus tank, there is a "tray" that one of the fittings taps into. It's been a couple of years since I looked, so I can't remember if it's the feed or return, but either should lessen turbulence issues. I hate to sound like a samba know-it-all, but I doubt VW would do it that way if it would cause any issues.

[babysnakes]

Skills my question came after reading this thread,

http://www.shoptalkforums.com/viewtopic ... 9&t=144818
The OP addresses a fuel return issue when fed through the top, also in this thread there is a pic of two barbs in the filler neck for the return, though I don't see why there are two.

On the other hand, If I put a tee midway on the 1/4" tube running atop my tank,




it would return the fuel at two points, cut the velocity in half and create less turbulence. Or so thinks me.

Mr. U, unfortunately, I only have a '72 tank in my '69, the '77 tank I had was total crap.

[skills@eurocarsplus]

I wouldn't sweat it too much.....don't overthink it. I think if that guy was getting crazy pressure he didn't have his tank vented properly.

I just welded a fitting to the top of my tank. granted, it has only been 800 miles, but so far, so good. I see you have your tank all dressed up. hope you have some touch up

I would say weld a nipple on your fill tube, but I don't think it will clear the hole.

[fl_buggy]

Sorry, I missed the 72 tank.

I can't see having trouble plumbing the return into one of the vent tubes. I'd just maybe try to run it to the left side so any turbulence won't be noticed at the pickup on the right side.

I can't see this setup working any worse than using a "T" at the pickup, and that seems to work fine.