Truly correct replacement gas tanks

[Duodec]

Fair enough, though they don't actually cover my question which is about current availability.  Following links are topics that discuss or show info about inner expansion tanks.

Topic 1  mentioned

Topic 2  pic of top of tank showing the rubber plug

Topic 3  same pic

Topic 4  mentioned

There were also topics on the old board (one at least of which was me asking about any correct repros back then).

Wonder how hard it would be to take a Spectra apart... or maybe see if Spectra will sell the tank in pieces, without welding the top and bottom together so an expansion tank could be fabricated and put in place. 

It really shouldn't be such a hard thing to reproduce... but cutting apart and rewarding a Spectra tank is fraught with peril (and galvanizing that makes the welding dangerous or you need to do a lot of blasting)

[cuda hunter]

I was thinking that purchasing an unwelded tank from Spectra would be the only way to go.
Easy to fabricate the system needed.
However, I can't say it will be easy to weld the tank together and end up with no leaks anywhere.  I'm no welder and that would be far beyond my comfort and skill level. 

Would be worth it to pay a welder for that service.  But then you need to dunk the entire tank in a stainless steel coating tank after doing that work. 
Sure makes a tank worth 6-700 dollars in the long run. 

Might be the only way to go about this with exception of finding an original tank that is not rotten or has any problems. 

[JH27N0B]

This thread may answer a mystery I've had since installing my Spectra tank on the '71.  When the car sits in the garage in warm weather and a full or nearly full tank, I've had issues with some gas leaking out around the filler tube grommet.  I assumed it was an issue with the new grommet I used when installing the tank, but now I wonder as the problem doesn't happen except in summer from what I've seen.
Sort of makes me wish I'd saved my original gas tank after I'd replaced it to restore, it was nice on the exterior but had corrosion on the inside.
As long as I don't fill up above 3/4 tank in the summer I never have problems with the leaking around the grommet.  I've had that tank on the car for about 10 years, everything else on the fuel system is restored to OE such as having the vent lines going into the vapor capture tube in the trunk, and the return line from the fuel pump, and the occasional leakage around the grommet in hot weather is the only issue with the fuel system I've ever had.

[Duodec]

What you described, along with gas spitting out the filler cap seal, are what I've heard about before.  Since I started with the Challenger in Las Vegas (118 degree summer days happen), once I found out about the expansion tank after the shop punched a bleeping hole in my tank, I decided I really wanted to get the same thing.  But factory tanks were nearly impossible to find even back then.  The only NOS one I ever saw in Hemmings (back around 1988 or so) they already wanted about $400 for; that was a ton of money back then and I didn't have it.

I guess I could consider rehabbing my original tank.  Outside was OK, inside had some rust but not terrible.  There's been no fuel in it for 17 years so should be safe to do a proper cleanup, get a patch welded onto the hole (though it is in a corner) and reseal the inside.  Maybe can get the specific paint they use in the good jerry cans; I've got 1950s European jerry cans that were obviously well used whose interior looks perfect.   

For moving the car around I actually JB-Welded a dime onto the hole; whatever tool they used created a depression that a dime fit perfectly.  Didn't leak for the remainder of the time I kept the car mobile.

[cuda hunter]

https://www.forebodiesonly.com/forum/threads/gas-tank-help.27425/#post-162851

[Duodec]

Mine's a 4-vent with the big vent tube that sticks into the trunk.

Classic wrote back about the stainless tanks.  No expansion tank.  Sounds like they were unaware of such a detail, which is unfortunate but not surprising.

I gather my question is answered.  Nobody makes a correct tank yet.

[71bs23V2]

Pics of the expansion tank from 1971 Cuda, production date of September 1970

[Duodec]

Very cool.  Thanks for posting that.

We just have to get one of the restoration parts places to start making the tanks correctly again.

As an option, instead of getting the unleaded tank halves from Spectra, I wonder if something could be done similar to the F.I. capable tanks with the pump and fuel connections on the top of the tank.  Cut out a square in the center of the tank top, form a slightly larger square to match the ribbing (like a form fitting patch).  I'd bet that a rectangular tank of appropriate size could be fabricated (thinking a stainless steel serving tray with slide lid) to mount to the underside patch.

None of its feasible for me right now but maybe a future project.

[anlauto]

My thinking is that the engineers back in the day thought it wasn't necessary so they stopped using them. The newer cars 72-74 likely never had them  (I don't know that for sure, since this is the first I've heard of them, or seen one in a 71 tank), but I know of the 50+ cars I've restored over the years, I've never had an issue using the tanks currently available.

[Duodec]

That may be true, and I don't know if the '72s or later had the expansion tanks, but '72 was a year of some cheapening across the Chrysler lines.  Simpler trim and grills, reduction of options... My favorite/least favorite example is the cheap universal side marker lights they switched to almost across the board.  Its also possible that the changed fuel tank venting in '72 alleviated the fuel burping problem that could occur.

[69BFan]

It is very unlikely that one of the restoration parts manufacturers would step in and modify the current production runs to satisfy that need.  It is not like someone would replace a good tank with an updated tank featuring the correct expansion tank.  Since a few manufacturers have started to produce a tank for EFI, then possibly they might be willing to modify the current setup to add the expansion tank.  But from the restoration side of the market, I am just glad that Spectra is still making a quality product for our old cars.