I was in the process of fitting an 88 tank into my 84 (and it's not all that complicated either. Some say it cant be done without major modding to the frame and bla bla. NOT SO) when I noticed something interesting.

Inside the tank (through the pump hole) I saw the filler and vent tubes. The vent is just slightly higher than the filler but it's also nearly 3 inches from the top of the tank.

By adding a preformed piece of tubing to bring the tip up about 1/2 inch from the top of the tank (any higher and it will force fuel up the evap vent line) you will add atleast a gallon more gas!

Theogre will probably sound off with a burb on possible problems with fuel expansion and fuel vapor info but I think that little tank on the right side will keep that under control.

I'll post some pics if anyone is interested in the idea and what it looks like.

im intrested !!

on my V8car, when the V6 was in there(its the car that travis: 1fst2m6 owned b-4 the cheetah) he had put in an LT-1 fuel pump, im gonna take that out Verry soon, when i put in my new Low pressure pump, and since the tank will be dropped it would be the perfect time to MOD it i wonder if the 86 tanks are close to the same?
whats the cap. of an 86, VS an 88?

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Rich
white 86 se, 2" drop, coil overs, KYB's. CRX intake, ported manifolds

Gold 86 se, Built 355, 4:10 adjustable Koni's, Eibach's,polly. and lots more!!

SOLD the Mitsu.

the 88 - 11.9 gal
the 86 - 8.5 gal
something like that?

Soaper

[This message has been edited by Soaper (edited 06-02-2003).]

84-87 tanks have a notch on the top of the tank. It keeps the bafel from being pushed back further to expose enough of the vent to put a hose on.

I was thinking there may be a slight problem. If fuel gets in the vent line (and it will) it will need to be cleared or the tank may not fill all the way to the top.

Most of it should clear during braking but I'm not sure how much and weather it will be enough. Hummmmmmmm...

A floating ball check valve at the bottom of the hose (where it attaches to the vent line) will do the trick.

wrong button

Soap

[This message has been edited by Soaper (edited 06-02-2003).]

84-87: 10.2
88: 11.9

do you have a pic of it modded?
what year tank is that?

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Rich
white 86 se, 2" drop, coil overs, KYB's. CRX intake, ported manifolds

Gold 86 se, Built 355, 4:10 adjustable Koni's, Eibach's,polly. and lots more!!

SOLD the Mitsu.

I had it modded but I took it off because of the drain problem. If the fuel blocks the vent line then the tank will only fill normaly.

The vent (and fill) tube is tilted down. At the rear the vent is about 2 inchs from the top, at the bafel its at least 3 1/2 inches. This will allow the vent tube to drain out.

If I put a sharp bend in it by adding a rubber tube it may not drain properly unless I put a float check valve in.

If I incline the the whole tube it will.

Anyway I'll make the mod that will work and post the pics.

OH! thats the 88 tank

[This message has been edited by 84Bill (edited 06-02-2003).]

i think you have a good idea here, if/when i get my tank out ill check into it

I think you'd be better off pluging off the old tube and drilling yourself a new one at the top of the tank. The way your bottom illustration is set up the gas will literally drain out of the tank as opposed to causing backpressure and stopping the fuel from coming in anymore.

-OR- perhaps put aa A shaped bend at the very top of the vent...

Then again, I may be totally off base.

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I can picture in my mind a world without war, a world without hate.
And I can picture us attacking that world, because they'd never expect it.
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01100100011101010110110101100010

quote Originally posted by Sootah: Also, how hard is the gas tank to drop? Is there a write up on it? It looked pretty straight forward while I was down there.

Hey Sootah , This thread may be of help .
http://www.mtsu.edu/~mkr2c/fuelpump.htm

Hope this helps .

Galen Smith
Red '85 Sport Coupe
Founder of Suncoast Fiero Club
Florida Fiero Council

If you find my advice helpful, then please take the time to give me a positive rateing .

I suppose drilling a hole in the tank and putting in a new line would work as long as the line gets cleared of fuel before the next top off.

In my observation the top of the tank is very close to the chassis and the clearence is less then 1/2 inch. The vent tube is atleast 1/2 ID.

It just seems to complicated to put in a new hole, block the old one and make sure the vent could drain properly. But hey go 4 it.

The important thing is understand how it works.

edit
Incidentaly the vent tube runs all the up and is attached to the the top side of the filler tube about 1 inch from the gas cap.

[This message has been edited by 84Bill (edited 06-02-2003).]

*Deleted my previous brain fart*

[This message has been edited by Steve Normington (edited 06-02-2003).]

I would think to leave thing alone due to possible leaks and whatever. Getting an extra gallon or so wouldnt be that big a benefit for me anyway. At 9 mpg avg, not much diff between going 100 miles or 110 between fillups,

If I'm reading this right... you are moding the air bleed that goes toward the top of the fill neck. If the air bleed is blocked then the air can only get out thru the main fill line. That can make it really hard to fill the tank at all with some pumps. As you've already found, you really want that line to drain.

Yes, you want to be carefull with the vent lines. Fuel can expand allot in hot weather. Way more than you might think. Especially when you fill a tank with fuel from a relativly cool underground tank in hot weather.

It's ok to do a tank alteration as long as the line can drain and it can't blow liquid up the evap vent. Dropping liquid fuel into the engine bay isn't a good thing. (POOF!:eek

GM's configuration may be a bit conservative but don't go to far the other way. The expansion tank might be enough but just be careful. You don't want to end up like that one guys that's toasted how many Fiero now??????

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Screamin' Yellow Zonkers... If it's Screaming and Yellow, I aint eatin it.

quote Originally posted by theogre: If I'm reading this right... you are moding the air bleed that goes toward the top of the fill neck. If the air bleed is blocked then the air can only get out thru the main fill line. That can make it really hard to fill the tank at all with some pumps. As you've already found, you really want that line to drain.

Exactly!

If I were to do this mod the only time I'd top off is when I'm setting out on a LD trip. Otherwise a normal tank fill (in my 88) is 9 to 10 gallons max when the needle stops swinging during acceleration and stops. It sure would be nice to have close to 2 extra gallons (60 miles!) on a trip.

I wonder if I'll look like a winston cup car pulling from the pits, you know, barfing fuel out the filler.

I doubt it though the damn hoses are sealed tight and a muthuhumpers to get off! The cap is vented but will not allow liquid fuel out. I don't think leaks be a problem at all. Expansion souldn't be to much of a problem since since there will still be an inch or so of expansion room and there is always plenty of room up the filler neck.

I'm gunna give it a whirl and see what happens, If you see smoke on the horizon you know the rest of the story.