Ok, my 48 is geting a efi magnum swap. I'm in question as to were would be a good place to tap into fuel tank to put a barbed fitting for the 5/16 hose. I was thinking about drilling a hole in the filler tube and thread the fitting in, then seal it up. I know i should drop the tank and weld a bung in it, but i dont want to do that if i dont have to. Any ideas from any one would be appretiated

imho the return should be submerged

I drilled a hole into the sending unit plate.

I used a piece of steel line and poked it through and then attempted to weld it around the hole.

now I realized, I should have used a brass fitting that threaded through the plate and put a compression fitting on one end and barbed fitting on the other.
so then you can used a metal hose inside to redirect the return and a hose on the outside.

Gotcha, i think routing it thru the sending unit would be a good option, and i wouldn't have to drop the tank

Use a bulkhead fitting to either go thru teh sender as mentioned or into a suitable flat spot on teh tank. Make sure the location allows you wrench access and make sure to use sealing washers - nylon, copper and a bonded-rubber are available. Watch what type of bulkhead fitting you get, as some only permit connections on one side, not both.

If going on the sending unit, make sure to choose your drilling location based on teh size of the nut vs other items - a sending unit isn't as big as you imagine when trying to fit a nut on the inside (not much room for drilling error).

If the returned fuel returns below fuel level it will have higher back pressure and it will vary with how full the tank is. Returning it above fuel level makes more aeration of it and higher vapor pressure in teh tank. It's a tradeoff IMHO.

If trying to assemble a home-brewed fitting from brass hardware-store items, consider that they are sometimes smaller in ID compared to a JIC fitting.

Try to point the returned fuel *away* from the pickup – returned fuel will be aerated and you don’t want that heading right back into teh pump.

My method is a BH fitting, with a -6 AN female hosebarb toward the engine, and a suitable piece of bent tubing (with a -6 nut and sleeve flared on) into the tank. If you work it right the bent tube route quite far from the pickup as it can be installed and tightened as you feed the sending unit thru its hole.

EDIT:
Mcmaster.com has this BH fitting in -6 but it's $30:
http://www.mcmaster.com/#50715K582
A hydraulic supply house would have steel fittings much cheaper.

Use your imagination, see what's available, and try not to get cross-eyed looking at tube, pipe, JIC and SAE thread types!

Good info fury fan, lookin like thats the direction im gonna go. Hopefully i have room on the sending unit.

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If the returned fuel returns below fuel level it will have higher back pressure and it will vary with how full the tank is.

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do you realize just how insignificant that is?

the static head pressure of water (specific gravity of 1) is .433 PSI per foot or .036 PSI per inch. the specific gravity of gasoline is around .75 so you multiply the above numbers by .75. that gives you .352 PSI per foot or .029 PSI per inch. even if there was a foot of depth in the tank that return line would only see .352 PSI of back pressure

Well what i ended up doing was sacrificing my gas gauge for now as it didnt work anyway, and made a new plate. drilled appropriate mounting holes then a 3/4" hole in the center. Welded a coupling in, put a barbed 90°fitting on top, and a fiting for a 5/16 inverted flare line bent towards opposite end of the tank on the bottom side. Should be good to go. Thanks for all the imput fellas...

Pic2

forgive me for being ignorant, but if that is your return, how are you getting fuel out? or is that in a different place in 48?

Theres a pickup to a bung in the bottom dr side of the tank. I assume this was factory but not 100%

i don't make this stuff up these are just basic fluid facts.

i didn't want to confuse anyone even further but the back pressure is actually to an extent canceled by the height of the liquid in the return tube,

as an example i'm sure people can understand that if the tube was only 1" higher than the level in the tank and you poured fuel into the tube then stopped the level in the tube would be the same as the level in the tank so in reality with regards to level there is no backpressure.

fluids exert pressure in all directions.

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I learned that in grade school by stomping on ketchup packets.

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some people aren't that observant in their application of the scientific method