So what I have been trying to figure out is what are the measurements of the fiero fuel tank for 87-88. I think I may have found a premade poly fuel tank that fits but im not sure on direct dimensions. Also would a poly be lighter than the stock fuel tank? 5lbs is 5lbs you know.

I'd be concerned about whether or not the poly tank would be structurally as strong as the oem tank. What about grounding issues? Have you checked with DOT?

I mean they must have been making poly gas tanks for sometime now and this is the 21st century so I would hope that they are structurally sound. I mean look at all the choices for poly gas tanks http://www.gastankdepot.com/plastic-gas-tanks.html as for grounding I assume just ground to the car like everything else.

Manufacturers have many variations of materials used for current model vehicle gas tanks. Some form of a polymer plastic is used in many of the tanks.

The Fiero has a very specific tank shape. It allows for the maximum amount of fuel to be stored within the dimensions available. I have no doubt about there being alternatives to an OG tank, but I would initially assume that other available tanks that fit within the dimensions available are slim.

Interesting thread and thought none the less. I would be curious as to where you go with this...

quote Originally posted by Tony Kania: The Fiero has a very specific tank shape. It allows for the maximum amount of fuel to be stored within the dimensions available. I have no doubt about there being alternatives to an OG tank, but I would initially assume that other available tanks that fit within the dimensions available are slim.

Good point... the real question is, is the new tank as big as the factory tank?

Supposing we're talking about polyethylene, it can be cut and welded (using polyethylene filler rod). So a slightly larger tank of approximately the correct dimensions could be made to fit like a glove.

I suspect that plastic fuel tanks are fluorinated; the tank is probably filled with fluorine gas (chlorine might work too) while it is still in the blow molding machine. This halogenates the plastic molecules, making them less porous, or more gas-tight.

I have a crappy plastic jerry can that always smells of gasoline, even when the cap is on. No actual dripping though. I suspect that it wasn't fluorinated.

At the places where you cut and weld, you would lose the fluorination treatment. For a project car, I don't think this would be an issue, but if you were trying to test a car for evaporative emissions, that might be different...

Im just assuming that a poly gas tank would be lighter. The question is what are the dimensions and weight of the current tank, I need to know these before I can begin my search. I currently dont have my tank off because my car is running ha so if anyone has this info would be good.

Many Aftermarket plastic tanks are likely test to meet FMVSS fuel tank rules and marked DOT etc on the labels.
Ground thru the "bulkhead" where FP and Gauge sender are installed. Likely Second ground at fill inlet to ground the nozzle to car.

quote Originally posted by Tony Kania: The Fiero has a very specific tank shape. It allows for the maximum amount of fuel to be stored within the dimensions available. I have no doubt about there being alternatives to an OG tank, but I would initially assume that other available tanks that fit within the dimensions available are slim.

Plus 87-88 tanks have expansion tank under right rear 1/4.

You could try installing a plastic tank in that space but very likely will hold < OE tanks.