1978 Eldorado fuel tank vs 1978 Sedan Deville gas tank - filler length?

[dennisspeaks]

Does anyone have the length of the fuel filler for a 78 Deville? I have been looking to replace my gas tank but no one is selling for the Eldog. I was just chatting with someone on fb that had said they replaced theirs with a 78 Deville some years back. I know the gas tanks are supposed to be different but I see the fuel sending units are the same.    It was suggested that a 78 Toronado might fit but the fuel sending units are different.  Any pictures of the 78 Eldorado gas tank, I would like to get a visual to see how they measure up.

I am going to give this a shot if I can get some measurements for the filler tube.

Thanks.

Dennis

[V63]

Image of 1975 eldo tank

[V63]

I have good used 77 SDV , 74 and 76 RWD tanks In Arizona 85004

[dennisspeaks]

Thanks V63, is your tanks for carb cars?  What is the difference between the 77 SDV and the 75 gas tanks?

[V63]

I

[V63]

The RWD tank appears to be the SAME
as I suspected...
however the filler is 8" longer
so Only that needs modification.

[dennisspeaks]

Well that is good news V63, you may just have solved the riddle for all of us Eldorado owners.

[dennisspeaks]

I just confirmed from another Eldorado owner who changed out his gas tank about 10 years ago on his 78 two tone Arizona brown one one, according to him the gas tank fit right in but the filler tube was longer and the license plate door didn't close all the way and he lost a few gallons of gas changing it to the Deville gas tank.

[dennisspeaks]

Since the gas filler tube is 6-8" longer on the Deville than on the Eldorado, how should I go about modifying it?

[79 Eldorado]

Dennis,
I do know that some tanks are sold without a filler which you can purchase separately. I've always been able to find one with the filler so not certain if there are some styles of attachment which make that more possible. The big advantage you have if you buy all new parts is it opens the possibilities up regarding attachment. You would never want to have someone weld a used tank for example. I would even recommend asking a welder before you buy a new tank.

You can make a wooden positioning "jig" using your original tank. That way if you remove the one which comes on the Deville you can then prep a replacement and position it using the jig. If it needs to be cut to be removed you may want to consider leaving something like a 3/4"-2 inches as it may make it easier to position and more stable when you add the new or shortened neck. You could shorten what you cut and then use an expansion tool for exhaust to increase the diameter of one or the other side so you have a nice lap joint to work with. If you expand the part you remove it may slip down far enough over the stub you leave that it would be difficult to see that anyone did anything special. Plan it out well because it the bends are the same shortening in a straight section will be by far the easiest (May mean leaving the entire bend when you cut).

Do you have yours out already? Maybe someone hear knows how the filler is attached. The example I saw advertised with a separate filler was when I was looking at '65 -'69 Impala tanks. I needed the '68 and it fortunately it came with the neck. The '68 Impala tank actually looks similar to yours but doesn't have the raised middle section like the photos I recall. The '68 tank is very shallow and a challenge for any aftermarket electric pump set-ups. Total depth is something like 6.5 inches as I recall.

Scott

[The Tassie Devil(le)]

Not sure what the aftermarket uses, but the originals have the filler fully attached.

Bruce.

[TJ Hopland]

I'm thinking all the GM cars that had the license plate fills had the neck as part of the tank.  It was the ones where the filler was somewhere else that often had it as a separate part likely just to make it possible to assemble it in the car. 

[79 Eldorado]

I suspect offering some without the filler for aftermarket was to reduce the diversity of PNs. I just "googled" the following words (without the quotes): "1978 deville gas tank" and some of the images are with a filler included and some are not. Maybe investigating 1978 Eldorado fuel filler neck should be the next step.

Just to check I opened a link with one of the ones, Deville, which comes without filler to see if it's listed for the Eldorado. If the fitment is correct the tank without the neck fits a lot of different vehicles but there are no Eldorados listed: https://www.carparts.com/details/Cadillac/DeVille/Liland/Fuel_Tank/1978/LILIGM4A.html

If Deville and Eldorado have the same bend, and the "only" difference is 2 inches in length, it seems like the easiest way to create something which fits with the least effort, also decent aesthetically, would be:
-Cut the Deville neck in a straight area
-Cut a section out, maybe an inch.
-Expand the remaining section ~1" so the cut/expanded section fits over the remaining section
-Slip the expanded part over the stub and weld the seam (everything needs to be new; never exposed to gas)

A slip fit will be easier to attach and will give you some ability to adjust the length to fit a jig prior to welding it in the final position.

Scott