Is it really worth shortening this filler neck?

[ootdega]

I went and got a fuel filler neck from a junkyard today, because I'm replacing the fuel pump and tank, and I was told shortening the filler neck would free up some tank capacity.

But now that I have it, it looks plenty short to me already. It only enters the tank by about 6 inches, horizontally at that. I'm not sure it's worth doing.

[IPreferDIY]

Unless you take a lot of long trips and always find yourself saying "Gee, I wish I could get a few more miles out of a tankful", I don't see the point of messing around with it.

[DerekTheGreat]

There seems to be plenty of room behind the diff and as if it would've killed Ford to sacrifice some volume in the trunk for volume in the tank. If only I could get 300+ miles out of a tank with combined city/hwy driving.

[gadget73]

You might get a couple gallons at most from it. The "big" capacity was supposed to be 21 gallons, and normal is 18 gallons.

[ootdega]

Okay, I won't bother with it then. I'll probably end up screwing something up anyway.

[johnunit]

That's the spirit

[DerekTheGreat]

LoL.

Big capacity is 21 gallons? That'll do. Is there another tank we can buy or is that what it's total capacity is? I can't ever seem to pump more than 13-14 gallons in it when empty.

[P72Ford]

I fail to see how shortening the filler neck would result in any significant increase in tank capacity?

The volume of a thin wall cylinder that protrudes into the tank is nil.

Speaking of cruising radius... My highboy has a 14-15 gallon tank and gets about 8 MPG around town. Nice.

My VW takes 13 gallons at most (believe its a 14 gallon tank), and I can go 600 miles (650 highway only). Lol.

[DerekTheGreat]

I think the theory behind cutting the filler neck back is to use the headspace volume that would normally be occupied by air. Caveat would at least include leaking as cold fuel warms up and expands in full tank.

[johnunit]

I fail to see how shortening the filler neck would result in any significant increase in tank capacity?

The volume of a thin wall cylinder that protrudes into the tank is nil.

Speaking of cruising radius... My highboy has a 14-15 gallon tank and gets about 8 MPG around town. Nice.

My VW takes 13 gallons at most (believe its a 14 gallon tank), and I can go 600 miles (650 highway only). Lol.

The idea is that the gas pump shuts off when the level hits the top of the mouth of the fuel filler tube. Raise the height of that, and you could theoretically get a couple more inches into the gas tank, in terms of the height/level of gas in the tank. Not sure how that'd work in practice with evap though.

[P72Ford]

If the tank is vented, fuel will always displace the air, until the fuel reaches the gas pump nozzle in the filler neck. If there were no safety on the pump, you would be able to fill the tank until gas ran out the vent, and eventually the neck, as that is usually the highest opening in the system. This all assumes you pump slow enough for the fuel flow into the tank not to be faster than the rate at which air exits the tank vent. Otherwise the fuel will rush up the filler neck and kill the pump.

The risk of potential leaks does not make this a worth while endeavor.

[DerekTheGreat]

Yup, Mr. Ventholes can't discharge the air faster than the gas coming down and so Click! Owners manual frowns on people like me who keep going until there's gas in the filler neck. Only on road trips though!

[gadget73]

Never really gotten the issues with tank capacity in these cars. by the time I need gas, I want to get out of the car for a few minutes anyway. Being able to drive for another 45-50 minutes would not make my life more pleasing on a long trip.

[IPreferDIY]

Ya, normally you'd stop somewhere on long trips, but I can see situations where someone would like to stop somewhere that doesn't have a gas station and defer getting gas until the next stop but they can't because they don't have enough to make it all the way. Even that's still only a very minor inconvenience.

[gadget73]

I get 250-275 a tank typically. Thats like 3 1/2 hours of driving. Long enough to want to stretch, pee, and hydrate.