Repro fuel tank with built in expansion tank

[femtnmax]

Do any of the repro fuel tanks have the factory style internal expansion tank?  My '74 repro tank does not, but does have the 4 vents for venting to charcoal canister.
I've noticed some forum members having fuel overflow from their gas tanks.  Some members don't fill the tank completely, other's drive 10+ miles after filling the tank to leave room for fuel expansion.   
I would prefer a true OEM fuel tank, but sounds like they may not exist.

[mopardave]

internal expansion tank? what are you refering to. none of the tanks that i have seen have baffles, or any other inner parts other than vent tubing. the spectrum tanks are oe replacements. sounds like it is not venting properly?
if you have the 4 vent nipples on the tank those 4 should go to a vent block on a challenger and the vertical tube for a cuda then upto the charcoal can.

[femtnmax]

internal expansion tank? what are you refering to. none of the tanks that i have seen have baffles, or any other inner parts other than vent tubing. the spectrum tanks are oe replacements. sounds like it is not venting properly?
if you have the 4 vent nipples on the tank those 4 should go to a vent block on a challenger and the vertical tube for a cuda then upto the charcoal can.

Dave, thanks for your feedback.  I was concerned because some forum members are having fuel drip out of the fuel filler neck, and I did not want this to happen.  I assumed the fuel tanks all had expansion chambers, but I am wrong....because after reading my '70 and '74 factory service manuals. the '74 says:
"...all carlines require a charcoal canister to store fuel vapors, and an overfill limiting valve, not all fuel tanks require a liquid vapor separator (challenger does).  Some models use an externally mounted separator (like challenger); other models are designed with an expansion dome on top of the fuel tank which contains an internal vapor separator tank."   
My 1970 factory service manual also shows an externally mounted liquid vapor separator.
It appears that the portion of the fuel filler tube that extends into the fuel tank acts to limit how full the fuel tank is filled, because when end of the filler neck is submerged in fuel, any additional fuel will fill the filler neck and not the tank.  Fuel expansion that causes fuel to overflow the filler neck could then suggest a venting problem.
So I am NOT going to eliminate my charcoal canister system, as it works with the liquid vapor separator to control vapors and provides a place for excess liquid/vapors to go.

[duodec]

My 1971 N95 car (kali emissions/ECS) has the expansion tank inside the fuel tank as well as the 4-point venting that runs to the vent tube in the trunk.  So far as I've been able to find out the expansion tank is not part of any aftermarket replacement tank, but I haven't looked for one in at least 5 years.  Sadly my original tank is not going to be usable so one of the repros is going to end up in the car.

[Alaskan_TA]

1971 tank with expansion tank;

http://www.hamtramck-historical.com/ServiceHighlights/_1971PassengerCarHighlights-02.shtml?load_img=22

[mopardave]

nice link, thanks always learning something

[LAA66]

 I don't think the expansion tank will prevent fuel from being pushed up the filler tube when the tank is near full. That is what the 4 tube vents to the vapor separator are for. Also the filler tube must breathe which is why a vented cap was used on N95 Challengers.

[FY1 RT SE]

I don't think the expansion tank will prevent fuel from being pushed up the filler tube when the tank is near full. That is what the 4 tube vents to the vapor separator are for. Also the filler tube must breathe which is why a vented cap was used on N95 Challengers.

That is exactly what the purpose of the expansion tank was.

[LAA66]

 In Barry's link it say's "An expansion tank inside the fuel tank prevents overfilling". Probably why mine burpes fuel if the pump totally fills the tank. In California most stations have the rubber vapor recovery boot which helps to keep the fuel somewhat contained.

 I still don't think a small cell can contain the expansion potential of gasoline.   

[duodec]

In Barry's link it say's "An expansion tank inside the fuel tank prevents overfilling". Probably why mine burpes fuel if the pump totally fills the tank. In California most stations have the rubber vapor recovery boot which helps to keep the fuel somewhat contained.

 I still don't think a small cell can contain the expansion potential of gasoline. 

I never had a problem with mine when it was a daily driver in Las Vegas; certainly the temperature swings there would be sufficient to cause some backflow if the system didn't handle it.  The gas tended to be cool (aka dense) when pumped; I could tell because the pump nozzles would cool down substantially when I filled the tank.  Then I'd drive an additional block or two to work and park it in the sun, on asphalt (only option) where it would sit baking all day on 115 degree plus days (hence the need for all new interior soft plastic parts...).

It never burped gas.

[femtnmax]

My 74 FSM has the answer, I just did not read it carefully:  On Page 14-58
"When the fuel tank is filled to the base of the filler tube, vapors can no longer escape, and they become trapped above the fuel.  Vapor flow through the vent line is blocked by the overflow limiting valve; and the filler tube is blocked by fuel.  More fuel cannot be pumped into a tank under this condition.  At any time pressures in the tank rise above the operating pressure of the limiting valve, about 1/2 psi, the valve opens and allows vapors to flow forward to the charcoal canister......
All carlines require a charcoal canister to store fuel vapors, and an overfill limiting valve, not all fuel tanks require a liquid vapor separator.
Some models use an externally mounted separator, other models are designed with an exapnsion dome on top of the tank which contains an internal vapor separator tank."
So the overflow limiting valve controls how full the fuel tank can be filled.  I'm going to keep the externally mounted vapor separator, and install the overfill limiting valve.  The book says the limiting valve must be installed in a vertical position to function correctly (page 14-60).
Hope this helps. 

[tommyg29]

just replaced my 71 cuda tank and the old tank has that box inside the top. Now I know what it was. Thanks for the information

[LAA66]

 I didn't know some expansion tanks had a vapor separator in them. That does make sense as the vapor pressure in the tank has to go somewhere and that would be a closed system such as the valve cover breather or charcoal canister. In the old days it went straight into the atmosphere. 

 Curious if the canister was a new pollution control design that was featured in 1974?