1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Mazda RX-7 '79 - Gas Tank Replacement

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Old Mar 20, 2007 | 05:46 PM
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Mazda RX-7 '79 - Gas Tank Replacement

need to now if anyone has Replace a sa tank with a fb tank
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Old Mar 20, 2007 | 11:07 PM
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I'm not sure am FB tank would fit under an SA. The SA had a full size spare, while the FB had the bicycle tire. The SA has a much deeper spare tire well than the FB. This shallower well allowed ~2 extra gallons of fuel to fit in the same spot.
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Old Mar 21, 2007 | 05:04 AM
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it won't fit at all. the tanks are ver specific to the year of the 7. you can only use tanks that fall into the range of years that were made to have the specific tank. for example, 79-80 tanks are the same, 81-83 are the same and 84-85 are the same.
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Old Mar 21, 2007 | 05:20 AM
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Ok Thank GUYS
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Old Mar 21, 2007 | 09:41 AM
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Yes, I have seen it done, The tank hangs down very low. I would not recomend it.
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Old Mar 21, 2007 | 06:44 PM
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What if you were to cut the spare tire well right oout og there and make the floor in the back flat? Would that allow the FB tank to fit?
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Old Mar 21, 2007 | 07:55 PM
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Maybe another option

I have been researching restoring and sealing the gas tank I think I will be ok with the POR 15 products but I also have inquired about getting the tank boiled.
A shop told me they have a process regardless of the condition of your gas tank where they pump a gas inside the tank if its rotted through they use a bladder and spray the inside with a fiberglass resin and the entire outside of the tank the inside seeps through pin holes or any leaks and bonds with the fiberglass outer coating and they guarantee it just an option you might want to look at.
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Old Mar 21, 2007 | 09:17 PM
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The tank itself rests on the spare tire well, with a foam pad in between to prevent squeaks and abrasive wear. Without the well, the tank may move and will most likely cause the hard fuel lines to rest against the bottom of the floor pan. The well itself establishes the needed clearance for the hard lines coming out ot the fuel tank.

It may be possible to fit a later tank with judicious trimming of the tire well. Another option may be to remove the SA well and replace it an FB one, however I think the FB well will be smaller in diameter than the SA one. Then one needs to get creative for mounting.

Another item to consider is making sure that there is no difference in center offset of the well in relation to the body. Have fun.

Due to the divider baffle in our tanks, a bladder is a no go. I also can't recommend using POR-15 inside the tank for sealing. There are other products that are specifically designed to seal the inside of tanks. Fiberglass is not a viable sealer as it will absorb fuel and allow the fuel to weep through it. Found that out on a custom Harley fuel tank I had many years ago.

Last edited by trochoid; Mar 21, 2007 at 09:24 PM.
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Old Mar 22, 2007 | 12:05 PM
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Por 15

So your telling me that POR 15 makes an Auto Fuel Tank Repair Kit and its not intended for fixing gas tanks.
One of the components in the kit named U.S. Standard Tank Sealer, and its not for gas tanks?
I have read several write ups on tank restoration using some of these products very detailed with great success. I think I will take my chances.
The fiberglass tank repair was performed on a 1974 AMC Pacer still running today with no leakes. I did not explain the entire process it was quite involved and the bladder was only used temporaly to support the tank if necessary while the chemicals were applied. There was also a gas applied inside the tank and it may not have been fiberglass on the inside but it was on the outside. I was just explaining a general overview of the process I would incourge more research if your intereseted it seems easier the cutting the floor pan out the car.
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Old Mar 22, 2007 | 03:27 PM
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When you stated POR-15, I took it as standard the rust converter/preventer, not as a seperate fuel tank repair system. I have to admit I have not looked through POR-15s product line and was not aware they had a seperate system for fuel tank repair.

Had you specified that there was a specific product for tank repair, I might have kept my mouth shut. LOL
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