A different sort of gas tank question

[russosborne]

Maybe I am up too late. But I had a crazy idea while reading here.

I have read about people removing the spare tire well and making a flat trunk floor. So far so good, I would be carrying a larger spare than would fit in there anyway.

Also read about using a fuel cell and centering it for easier exhaust. That is where my first idea came into being. I was thinking why not just use the stock tank and center it? Well, after seeing pictures of it the top isn't flat, so I can see that being a serious issue.

So my next idea is what about a tank out of another car? One that does have a flatish top.

So my real question is has anyone else thought about doing this and if so do you have any tanks in mind that could work? Right now I am not too concerned with the fill tube.That can be worked out. Also, having a custom tank built would most likely be far too expensive for my budget.

It must be mounted under the trunk floor. I used to have a 69 Stang and I don't like the idea of the top of the tank being the trunk floor. When I was a kid I didn't know better, but I do now. The fuel cell idea used to be one I wanted to do, but after reading about the lining not lasting very long I would rather not go that route. Although I may end up having to, but it will still have to be mounted under the car. I really want enough trunk space for a 15 inch spare, jack, a small tool box, and a battery. That doesn't leave much room for anything else.

Thanks,
Russ

 

[78CobraII]

Yup, I remember the tank in my '65 Mustang. It was a bomb waiting to be hit. Of course any rear mounted tank in any small car is a safety issue. GM even had a few fuel tank-related deaths with its early 80's Malibu family of cars, and that's a mid-sized car.

For any replacement tank, the fuel fill really is the big problem, with mounting coming in a close second.

The Pinto gas tank (and MII by association) really has some safety issues, but it was much more of an engineered system than the tanks on earlier Mustangs. Any replacement gas tank (on a street car) has to take a lot of things into consideration. Racing is actually easier as there are fewer considerations like where to run exhaust and where to place the spare.

Rear mounted tanks like on the MII are engineered to slide forward during a big rear impact and slide on top of the rear diff without crushing or tearing. That's where the Pinto tanks failed, they tore on the sharp edges of the 6.75 inch rear diff cover and the body seams opened, allowing vaporized fuel into the passenger compartment. The 8 inch rear was not a problem due to its smooth shape. The plastic shield on the front of Pinto and MII tanks is meant to keep the tank from tearing open on the diff. Ford's real malfunction was that it put profits before public safety when they discovered the problem.

Some have proposed a rear-fill mod for the MII, but I hate the idea of the fill tube running through the trunk like on the early Mustangs. If you do that you really need a firewall between the trunk and passenger compartment like most racing regulations call for.

I have been thinking along the lines of using an inexpensive plastic fuel cell wrapped with a heavy gauge sheetmetal shell. You still have the issue of fill and mounting to solve though. Plus it will be tough to get a large enough tank to match or exceed the factory tank size.

The fill could use a 90 degree fitting coming out of a top mounted roll-over proof fill valve with plastic hose runnning to the factory fill location. That would allow the tank to fit close to the trunk floor. You would need to weld attach points for the new gas tank straps to the trunk floor or frame. The new trunk floor (minus the spare tire well) would need to have bends running from side-to-side across the trunk so that a big hit would collapse the floor rather than moving it forward where it might cut passengers in half.

Serious stuff, and once you mod it, you are responsible for it.

 

[russosborne]

Yeah, nothing is ever simple.

I am planning on a firewall anyway, more just to keep the battery acid in the trunk if it ever explodes. Plus it will really help solidify that part of the car. Planning on a 6 point cage anyway, so who needs a rear seat?

I was thinking I could just cut out the spare area and weld in sheet metal there, leaving the rest of the trunk floor stock. I haven't really looked yet, wouldn't be doing any cutting until after I get any rust repaired, want to leave as much solid metal on the car as possible until after rust repairs are done.

I really wanted to run dual exhaust (one on each side) but maybe there is too much involved to make that worth while.

Course, I really need to make sure the car is saveable before I get too carried away. Actually, I am sure it is, just not sure it is doable by me, and that is important from a cost standpoint if nothing else.
Sometimes I wish I was back in Arizona where rust is something you just hear about from far away.

Thanks,
Russ

 

[DOZZ351]

REAR FILL

I'VE BEEN WANTING TO DO THE SAME W/ MAYBE A 69-70 TANK.
IF ANY BODY HAS PICS I WANNA SEE EM.
ANY OTHER II MODS...

 

[78CobraII]

The '69-'70 tank still has the issue of the rear fill location. Plus its engineered to drop into the trunk and mount around the lip with screws. With a car as small as a Mustang II (or any Mustang for that matter), a trunk-located solid-mounted fuel tank is a safety issue.

If I was going to replace the fuel tank in a MII with something custom, I would cut out the spare tire well and weld in a flat sheet in its place. Then I would find a fuel cell that would hang under the car but would have room to slide forward over the rear axle in case of a large rear impact.

 

[LILCBRA]

Been a while since I was last on. I will give the suggestion that I did for my tank problem. I used a fox body tank. The top shape is the same general shape as the II tank and physically fits. The hump in the top is smaller than the II tank, so cutting out your spare tire well and fabricating something larger to accommodate a larger spare is doable. It does take some fabrication to the tank to do this, and if anyone remembers the old posts from a couple years ago, there really isnt any room to run duals out the back. But, if you are interested, here is a link to the thread about it. If you have any questions about it, let me know, and I will try to answer.

gas tank is giving me fits..... - Mustang Forums at StangNet

 

[COBRA 7]

Yeah, nothing is ever simple.


I really wanted to run dual exhaust (one on each side) but maybe there is too much involved to make that worth while.

Thanks,
Russ

Check out the duals I built.

http://www.stangnet.com/mustang-forums/attachments/19581d1078279679-exhaust-exhaust3.jpg

 

[russosborne]

Nice.
I was hoping to run them out the back. Not sure how legal side exits are here in Ohio, there is a law about "tampering". For ex. you can't put dual exhaust on a car that didn't have that option from the factory.
Granted the '76 won't have to be emissions tested, but police seem to like to pull you over around here for any reason they can.
Russ

 

[kcobra302]

keep in mind some II's did have a true dual exhaust, it had a couple of resonators and just terminated into a single muffler with dual ins and outs.

 

[Wart]

Nice.
I was hoping to run them out the back. Not sure how legal side exits are here in Ohio, there is a law about "tampering". For ex. you can't put dual exhaust on a car that didn't have that option from the factory.

Really?

If they enforced that law it would be the first time I would have heard about it.

Far as 'side exhausts', as long as the exhaust terminates outside the body of the vehicle your OK.

Mine ended outside the rear tires. Looked like curb feelers. Kept the tires from getting heat. Got ribbed about it a bunch. To hell with it.

Granted the '76 won't have to be emissions tested, but police seem to like to pull you over around here for any reason they can.
Russ

Same here as everywhere.

 

[russosborne]

Yeah, it is there. Not sure about enforcement though. I read it when I first moved back here about 4 years ago while reading up on the emissions and registration stuff.
Akron may not be a problem, but I work in Solon, and lately they are really trying to give out as many tickets as possible up here. So I just want to make sure I am ok. Of course, I may be retired before the Stang is running.
I knew that the II's came with duals sometimes, but was just using that as a reference point.
Russ