rear tank - fill neck venting
 

I have installed a FuelCellGuy rear fuel cell with my swap. There is a vent line that comes out of the passenger front of the tank by the fuel pump. I just hooked a rubber hose to it and have it vented to atmosphere. There is a 3/8NPT bung that is labeled filler vent. Typically we see these ran by to within an inch of the cap. Is this necessary and why? Can it not just be vented to atmosphere towards the back of the tank just like the other side? I really don't understand the difference...
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Re: rear tank - fill neck venting
 

I have done it both ways. Never had problems, but make sure you put something like this at the end of the vent tube you are using so that crud doesn't get in your tank. The only issue with this is in the event of a roll-over the fuel will likely spill out of the vent. If there is a roll-over check ball in the tank on this port then you are fine. If you aren't worried about a roll over then your setup (with the filter) will function fine as far as the engine is concerned.

http://www.knfilters.com/images/cran...erubbertop.jpg

Re: rear tank - fill neck venting
 

I suppose you could do it any way...including the way you're doing it.

I'm guessing that the 3/8" filler vent would be plumbed to the gas filler and the other line would be run to a charcoal filter and then to the solenoid on your intake manifold.