Posted: 19 May 2010 at 9:07pm | IP Logged

during my many searches on the fiero I ran across these schematics to build a 15 us gal fuel tank that supposedly fits into the stock tunnel, I think that it should/could be a great build for any of the v8/3800 guys

2010-05-19_210740_Andy-fuel_tank.zip

Posted: 19 May 2010 at 9:18pm | IP Logged

more info:

SE Center Fuel Tank

By Endre R. Bujtas

The object of my design was to fabricate a replacement Fiero tank that would:
1. Have a larger capacity
2. Fit inside the '88 tub well
3. Allow filling from either or both sides of the car.
4. Allow the fill nozzle to be placed where it would not interfere with the V8.

Attached are the drawings of the center fuel tank. There are 2 groups of drawings, 1 set is for the design and the other for the fabrication.

The pump suction fittings were placed up front since that is where my fuel pump is located. My car will sit with a slight forward rake so that the fuel will flow towards the front of the tank. The only drawback to this design will be under hard acceleration with a near empty tank. However, the large capacity of the fuel filter (Mallory Comp 500 model 3500) should take up some of the slack for those periods. I measured the capacity of the tank myself and got a little over 15 gallons with this design.

The tank was designed using 2 AN-16 fill fittings. These fittings are connections to the two side tanks. This design could be adapted to allow a fill pipe to be used instead of AN fittings. In this case, I would recommend using a 90 degree elbow placed inside the tank with only a small 2-2.5 inch straight section protruding out of the tank. This way an individual will have the capability of using a fill hose and the pipe inside will act as a splash guard. Also, the individual will have the option to place the fill on the right side of the car, if he/she chooses. Having the fill in the lower area prevents the fuel hose from coming near any rotating part of the engine - if you are using a longitudinal setup. And allows for easier routing of the fuel fill hose or pipe.

The tank is designed with 2 baffle plates, which also add structural rigidity to the tank. The baffles have the corners cut out so that fuel can go around them. If one wishes, they could add another baffle plate that extends longitudinally down the front. I wouldn't put one in the back since it will interfere with the VDO sending unit.

The tank is designed to use a VDO fuel level sending unit. It has a very low profile, but even then you will need to bang a small indentation in the tub well to clear the sensor wire studs. I used a ball-peen hammer to make a small dent. This tank will take up most of the room in the well. It is loose enough to fit inside the well, but I added foam rubber weather stripping to cushion the tank. This makes for a tight fit. You will also need to cut out the plate at the rear of the well to make it a full tunnel. This tank just about exits the tunnel. It is designed to end on the same plane as the rear firewall. The tank is longer than the stock one.

The design of the tank allows the reuse of the Fiero fuel tank hanger T-bolts. But I think I had to make a longer T-bolt for the front bracket. You can not reuse the original Fiero tank straps. I made a replacement out of 1/8 x 3/4 flat stock. The bottom of the tank is flush with the bottom of the Fiero tub so that a straight bar was only necessary. The rear of the tank is supported by a 3/4 x 3/4 square tube that is welded across the chassis. This adds additional stiffness to the chassis as well as support for the tank. The tank is attached to this bar with bolts. Tabs welded to the tank keep the tank firmly in place. I also added foam strips on the bar and straps. The tank is fully cushioned.

The tank can be made out of either sheet steel or aluminum. My tank is made from 3003 aluminum since I wanted a light tank and 3003 does not make those small cracks when bent. The tank is made of sections that are bent and welded together. You will need a sheet metal brake to bend the sections. A clever person might be able to make their tank with one sheet for the bottom and sides. This way only the top piece (and some side corners) will need welding. I also filled the forward and center section of the tank with fuel cell foam. But watch out when welding since this stuff is not fully fireproof. I recommend making the tank out of 16 ga or 18 ga steel sheet metal. This is easier in terms of welding. Sheet aluminum requires TIG welding by an expert. If you are making the tank out of steel, then I suggest coating the inside of the tank with a sealer when you are finished. Eastwood sells a fuel tank sealer. This will help prevent the tank from rusting. Or you could fabricate the tank from stainless steel. This would be a bit expensive, but you'll never have to worry about rust.

If you are making a steel tank and want to use AN fittings, you will have to get steel weld bungs. After the tank is fabricated, you should pressure and leak check it. I blanked-off all the fittings and made a single hose fitting to the AN-6 recirc connection. The tank was pressurized to 30 psi and soapy water placed over the weld areas to check for air bubbles. Any leaks were rewelded and tested again. I also did a capacity test. I measured the tank capacity by filling the tank with water using a known capacity container - 1 gallon milk bottles. I set the tank on horses (placed at each end) and filled the tank with water. Water is a bit heavier than gasoline so I wanted to check that the tank will support the weight fully loaded. I also observed and checked for any leakage from the seams. As a matter of fact, even after the tank passed the air test, I did have a small fluid leak from one of the welds at the seam which had to be repaired. So, I recommend doing this test as well.

Posted: 22 May 2010 at 12:17pm | IP Logged

Would the fibreglass like the gasoline though? Isn't it pourous?

Personally, I think it'd be cool to do it up as a fuel cell, rather than a fuel tank.