fill tube dia?

[55metalmonkey]

Just looking for some input for a fill tube dia. generally I stick with a stock size but this situation is a little different.
I'm going to put a fuel door on the right side fender out of a 80's van like a few other guys have done, this will have the fill and a vent line but it is going to a RCI poly fuel cell. it's a top fill style so I will have to make a new plate for the top and extend a full tube over to the fill door.

I would like to keep the tank as high as possible so after all that bla bla bla the question is : does anyone have any idea on what the minimum recomended tube size would be for the fuel fill tube? I know bigger= better but in this case the smaller the tighter radius bend I can get. I don't want to have the issue of the fuel tipping the stop on the gas pump everytime I fill up. IMO 1.25" looks to be the min but if anyone has done it with smaller and didn't have a problem I'd like to know.

Thanks

[OrrieG]

Not a petroleum engineer but I would guess most fuel dispensing pumps are designed for 1.25 to 1.5 inch diameter inlets. The dispensing pipe is obviously smaller but the fuel is under pressure, after it hits the fill pipe it is all gravity. Tight turns will reduce flow too. You could go smaller but it depends on how impatient you are!

[55metalmonkey]

pretty impatient, , I'm not a petrolum engineer either but here is my theory.... Theorys have been known to be wrong btw. The gas nozzle form the pump is 3/4, I could get away with 1 1/4" tube if there is a 1/2" -5/8" vent from the tank , most fill tubes that I've seen seem to be 2"+ but several slightly modern cars that I've seen (2000 or so) have standard size necks which hit a transition to a smaller size after the vent. wondering if I could get away with the same idea.

Then again whats the worst that could happen, slower fill ups? get POed and tear it all apart do it again.

[chev3600]

Maybe a larger vent line to go with the smaller (1.25-1.5") filler? I just saw one on a newer chevy Colorado and the filler looks like 1.25 and the vent is only 3/8. But I'd still go at least 1/2". Are you using the vent tube on the neck or adding a vented line to the cell?
Posted via Mobile Device

[55metalmonkey]

I'm planning on using the vent line on the neck and running it to the top of the cell with a splash baffle, not that it's a big deal if fuel burps up the vent... it will just flow back down to the cell but I might as well put it in. I was thinking 1/2" anyway since I have the tube and bender for it, I'll have to scope out some 1 1/4 and see if it will do as tight of a radius as I want.

[55metalmonkey]

FYI, in case anyone had the same question as me
Finaly found the answer, 1" is about the smallest I could go but would have to increase the size of the vent to 1/2"
original is 1 1/4" with a 3/8" vent tube for behind the seat style