hey guys.I have another question..this time it is about gas tanks.I have several cars,85-88,I am taking the goods from all of them and replacing the bad parts.any way would a 88 4cyl tank fit a 86 2.8.thanks for any info

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David Eric Jenkins

They got about one gallon bigger in 88 and I think 87 too, but they should all fit in the frame space provided.

thanxs i thought they were bigger but did not know.....but now i know

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David Eric Jenkins

84-86 are the same 10.5 gallon, 87-88 have a 12ish gallon with the expansion tank near the battery. You can put a larger tank in an older car.

It will fit but as I heard, you may also need to swap the straps for the tank also.

Steve

quote Originally posted by JumpStart: It will fit but as I heard, you may also need to swap the straps for the tank also. Steve

yup, I have heard this also.

The tanks will fit, but it's not a direct plug and play. The pinch weld/seam on the tanks are in a different locations and the chassis mount locations for the t-bolts and straps are different between those years. There are several different solutions some cheap, some more expensive and none of them are too difficult, longer tanks straps, longer t-bolts, BFH, welding new mounts. Do a search for tank swap and read about all the different solutions.

if you're going to use the larger 87-88 tank in an 84-86 you also need to swap in the expansion tank as well as the above mentioned items, otherwise when the tank is completely full, you'll have a potential bomb on your hands, especially if you live anywhere it gets considerably hot

[This message has been edited by av8fiero (edited 04-11-2011).]

thanks for all the info..everyone has gave me some things to think about......beleive i will just keep the tank from an 86

I'm doing the tank swap right now so please explain the potential bomb theory to me. If all you do is replace the smaller with the larger and you hook the vent line up to the charcoal canister you should have vent operation just like the stock smaller tank with a slightly increased capacity. Though not as much as if you installed the expansion tank. I have it, just not going to install it right away. Now if you capped the vent completely, I could see that being a problem since fuel vapors wouldn't have anywhere to go.

I have both tanks sitting side-by-side on the garage floor and I measured the height of the fill tubes from the floor and they are roughly the same (within 1/8") so I don't think that would affect what we're talking about. Could it be the sending unit itself? A difference in the vent mechanism in the top of the sender? Mine is a replacement from the Fiero Store which they say fits all years for the V6 so I'll rule out the sender in my case. What am I missing?

Just glancing, the 88 tank appears to be about an inch longer overall and seems to have a slightly larger cross-section because it was alot harder getting it to fit in the tank well. I had it in once already but had to pull it back out because I forgot to put the straps in their slots. I had to remove the clamps for the heater and AC lines so I could free up some extra wiggle room going in/out. I also had to pean-over the weld lip on the tank wherever it looked like it would catch on the heater line brackets. They point up, the tank lip points down so they tend to hook real nicely together. I'll let you know on the straps, the pre-88s actually seem to be the longer ones. The earlier T-bolts are also slightly longer.

Gary

The main difference between the 84-86(10.2 gallons) and 87-88 (11.9 gallons) is internal. The 84-86 tanks have an internal expansion area. The 87-88 tanks are external via the extra expansion tank mounted under the passenger rear fender. The problem isn't just vapors on the 87-88 tanks. It can actually be liquid fuel.

With a complete fillup on a hot day you may see some effects. The pressure most deffinately can build up, though I think a bomb is a bit eggerated (with a proper ignition source, tons of beer, and the need to actually see a fiero on fire... maybe ). One bad thing that can happen is that expanding liquid fuel can go into you vapor canister (where else would it go, right?). Can we say saturated? You don't want to have to replace those too often. It only take a little bit more time to do it right. If the pontiac engineers decided it needed one I think I'd have to agree.

Mounting the 87-88 expansion tank on 84-86 fieros:

Remove passenger rear wheel and inner fender. Hold up expansion tank and mark the 2 botton holes to drill. Mark 1-2 more holes for your lines to a from the X-tank. Make sure these go under your battery box if you have one and put in a rubber gromet. This will keep the lines from rubbing on the sheet metal. Drill your holes and mount the tank. Run your lines through your holes. 87-88 fiero have a cutout under the battery box already. 84-86 do not, hence the need to drill the holes for the lines.
There is one more mounting hole on top of the x-tank. You have to remove the rear clip to drill a hole for this one. Its not necissary to have it. It can be a real pain to get to on your donor also. Hope this helps.

[This message has been edited by Fieroseverywhere (edited 04-11-2011).]

Well maybe bomb is quite a bit of exaggeration, but it will definitely be a fire hazard. if the fuel would get warm enough it could expand enough to push fuel out through the charcol cannister, ruining the cannister, and puke fuel into the engine bay, not a good thing. Add a little spark or some exhaust heat and you'll have a toasted fiero