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  1. #1
    FEP Power Member vintageracer's Avatar
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    Default Tell Me "What's the Difference"????

    I have heard from any number of knowledgeable Foxbody guru's that the 1979 Mustang carburetor gas tank is different from the 1980 up carburetor gas tank yet none of the guru's can tell me what is different between the 2 gas tanks. All they tell is that it's just DIFFERENT!

    Therefore my question:

    What's different between the 1979 Mustang carburetor gas tank and the 1980 up Mustang carburetor gas tank?
    Mike
    Remember, "Drive Fast, Turn Heads, Break Hearts!"

    1995 Ford Powerstroke F350 "Centurion" STRETCHED Crew Cab Dually

    I like "Cut & Coach Built" vehicles!

    www.musclecardeals.com


  2. #2

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    The clearance on the passenger side. You can't run a tail pipe on that side on a 79. And secondly the capacity. The 79 is a 12 gallon tank while the later is a 15 gallon tank.


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    Tony

  3. #3
    FEP Power Member vintageracer's Avatar
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    Will a later 15 gallon tank bolt in a 1979 Mustang to replace the original 12 gallon tank without any modifications?
    Mike
    Remember, "Drive Fast, Turn Heads, Break Hearts!"

    1995 Ford Powerstroke F350 "Centurion" STRETCHED Crew Cab Dually

    I like "Cut & Coach Built" vehicles!

    www.musclecardeals.com


  4. #4
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    82GTforME's Avatar
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    Default

    I wished I had all of the details on the differences. Our recently passed friend Travis had told me similar things about putting in a "later" tank. Sheet metal changes under the trunk somehow for the extra capacity. IIRC you can beat the sheet metal up somewhere and it will work. Unfortunately I do not have more details than that right now.
    For the T5? I'm jealous, I would have loved that car but glad you bought it.
    Quote Originally Posted by Travis T View Post
    I think this is my favorite car on the site right now.
    Quote Originally Posted by BLUECRAPI
    This is the best thread on the internet.
    Darran
    1982-1C (Black) GT T-Top:http://vb.foureyedpride.com/showthre...he-Road-Thread
    1986-9L (Oxford White) SVO: http://vb.foureyedpride.com/showthre...d-did-1986-SVO
    1979 (85:Tangerine) Coupe (my son's): http://vb.foureyedpride.com/showthre...gerine-Machine
    1979 (3F:Light Medium Blue) Coupe (one day to be my other son's!) http://vb.foureyedpride.com/showthre...um-Blue-Bomber!

  5. #5
    FEP Power Member vintageracer's Avatar
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    T5?

    Yes!

    As is standard procedure in salvage yards they "punch" the gas tank to drain the old gas and Skip tells me this T5 gas tank is no exception. My plan is to "try" to weld up the hole in the original gas tank IF is is usable and not rusty inside beyond belief unless somebody out there has a nice used 79 gas tank.

    I'll find out when the car shows up here in "Hillbilly Hollywood"!
    Mike
    Remember, "Drive Fast, Turn Heads, Break Hearts!"

    1995 Ford Powerstroke F350 "Centurion" STRETCHED Crew Cab Dually

    I like "Cut & Coach Built" vehicles!

    www.musclecardeals.com


  6. #6
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by vintageracer View Post
    Will a later 15 gallon tank bolt in a 1979 Mustang to replace the original 12 gallon tank without any modifications?
    Three things.

    1. There was spill over from Fords emply boxes of stock, so many 1981 cars, like my old 6 cylinder, still got the smaller tank wth the earlier fixing/securing strap parts. The nominal 12.4 US gal tank then got replaced by the nominal 15 US gallon.

    This March 1981 car was still listed as 12.5 gals.

    http://www.ascmclarencoupe.com/Liter...arch1981_2.jpg



    2. From all the posts here on FEP, the tail pressing was reprofiled for the potential of one Thunderbird style 220/55/vr 390 spare tire; as they cleave together, the fuel tank was reprofiled as well. First the notch trunk was reprofiled for a few extra 16ths of deck height, then the floor, then the window wiper on hatches was removed for extra SSP tire space. When you rupture a tire or get a flat, its dang hard to fit everything back in the trunk that normally just holds a steel rimed 185R14 on 1, so Ford did quite an amount of detail work getting the bigger tank in.

    The tanks interchage with effort, one area needs relief space with a big friendly hammer. The tank securing is more risky, but it can be done. The best option is a fringe clip and swap. Drop the bumper cover, and have the later tangs partly stich and partly butt welded, but not full circuit, then tamp in and use some honest filler in so they don't tear out the welded section in a bad shunt.




    The tank top shape differs, and the holding tangs differ. All rear tank Foxes have a Pinto style RIM moulding shock absorbent "flak suit" to stop axle to tank sparks in a big shunt funt. Just make sure you use the E1 coded stuff if you are making the change.

    I like the 22 (83liter) Glens Tanks myself. They are able to be indexed with a reverse stage CFI and later type fuel gauge, and the EFI stillage pot and primary and secondary stage is all incorporated with modern EFI pumps.

  7. #7
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    82GTforME's Avatar
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    The only info I have that I recall for the tanks.

    Quote Originally Posted by Travis T View Post
    79 and 80 most definitely had smaller tanks. I have seen threads on FEP about doing the swap.
    Quote Originally Posted by STL79Coupe View Post
    They are 12.5 gallon tanks and you can get new tanks for the 79-80 made by spectra if I remember correctly. The later tanks will fit but you have to massage the trunk floor for the hump in the newer tanks. You also have to move the straps or lengthen them something like that. You can get Rockauto for $167 but only 4 remain from what it says. Autozone list them for $278 or something.
    Quote Originally Posted by Travis T View Post
    I think this is my favorite car on the site right now.
    Quote Originally Posted by BLUECRAPI
    This is the best thread on the internet.
    Darran
    1982-1C (Black) GT T-Top:http://vb.foureyedpride.com/showthre...he-Road-Thread
    1986-9L (Oxford White) SVO: http://vb.foureyedpride.com/showthre...d-did-1986-SVO
    1979 (85:Tangerine) Coupe (my son's): http://vb.foureyedpride.com/showthre...gerine-Machine
    1979 (3F:Light Medium Blue) Coupe (one day to be my other son's!) http://vb.foureyedpride.com/showthre...um-Blue-Bomber!

  8. #8
    FEP Super Member STANGMAN116's Avatar
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    Hey mike let me take a look at my 79 tank before she leaves.. give me a shot on my email if interested.

    Stangman116@yahoo.com

  9. #9
    FEP Power Member 81coupe's Avatar
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    Mine started life as a 81/ 2.3L and also has the 12.5 Gallon tank. Sits just like pic posted above. I now have full dual exhaust and have no clearance problems. The tank just sits a little more to the Passenger side.
    1981 Mustang Coupe: Rebuilt 91/306, Ported E7's, TF Spring kit, E-303 Cam, RPM Intake, Eddy 1406 Carb, FMS Dual Roller Timing set, March UD pulleys, Summit LT Headers, Summit 2-1/2" Chambered Mufflers w/ 2-1/2" FlowTech H-Pipe/ Flowtubes & 2-1/2" LMR SS Tailpipes. C4 trans with 8.8/ 2.73 Rear.

  10. #10
    FEP Super Member xctasy's Avatar
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    Mr Basin Motorsports from Sprague River, OR

    79-80.5 Carb fuel tank verses later EFi fuel tank

    Quote Originally Posted by Basin Motorsports View Post
    Before I hauled off the crashed notchback, I spent a few minutes documenting the difference in the carb vs EFI fuel tanks. I see this question pop up once and a while and hopefully it answers a few questions.

    .....

  11. #11

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    Edited
    Last edited by Stash; 01-15-2018 at 10:03 PM.

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