bed mounted aluminum tank and two bottom nipples
 

ok guys, building the 69 from ground up and have a 5.3 im building to put in with injection and was wondering the two nipples on the bottom of the bottom of the tank, one is for feed line and other, use it for return line? i have a nipple on the top but i use that for a vent.
Thanks in advance for any help

Re: bed mounted aluminum tank and two bottom nipples
 

whose the tank manufacturer? ..are you running a intank pump or external? or how are you doing your fuel pump setup?...pics might help

Re: bed mounted aluminum tank and two bottom nipples
 

Typically both of those are outlets. Not a good idea to use one as a return. Just cap off the one you do not use.

Does the tank only have one fitting on the top? Would not be hard to ad another bulkhead fitting to the top of the tank for the return line.

Re: bed mounted aluminum tank and two bottom nipples
 

Its for dual feed. Thats the low point on the tank, so putting the return there would make the return fuel fight the pressure at the sump from the weight of the fuel.

Re: bed mounted aluminum tank and two bottom nipples
 

I'll be running an external pump to the LS. I had the idea to install another fitting on top, but others are saying that this is bad and causes bubbles in fuel that cause issues with fuel injection. They LSX forum say to use the two bottoms as one for in and on for return, illuminating bubbles in fuel.

Re: bed mounted aluminum tank and two bottom nipples
 

IMO, they say that because they read it somewhere on the same forum. Yes, I know the "Bubble" thing, but after lord knows how many vehicles being built and tuned...from 350hp to 1500+, I have NEVER had a vehicle see a failure related to bubbles in the fuel.
Theoretically, if you had like a 1L tank where there was no fuel volume, it would be possible to create bubbles that somehow got sucked into the pickup, and forced into the lines....but that would have to be a tiny tank, and a LOT of bubbles. Surface tension on gas is low, it doesnt' bubble well.

The last tanks I've purchased all had 2 ports on top, 2 on bottom. On upper for return, one upper for vent w/rollover check, the sumped 2 on the bottom for feed.

Re: bed mounted aluminum tank and two bottom nipples
 

my new aluminium tank has the filler tube, sending unit and one nipple on top then two nipples on bottom.