As some of you know I have been working on a bigger tank for my 87 GT. I finished the tank and tested it for leaks about a week ago. Originally I had calculated the tank would hold about 19.7 gallons. I had planned to use about the same amount of air expansion space as the factory tank. I lost my nerve for fear the expansion area wouldn't be enough and made it larger by 240 cubic inches then my original design. I should tell you this tank has a box baffle similar to the stock one, stock fill, vent, and check valve along with an extended pick up, pump mount and wiring. The pick up sits in a sump about 1/2 inch lower than the rest of the tank. This means I should be able to use most if not all the gas. It also means I can use the stock expansion tank and charcoal canister. Pretty important features to have. The new tank holds 18.7 gallons and has a larger expansion area than it probable needs. To all of you that told me it couldn't be done - guess you were wrong. To all of you that gave helpful suggestions you have my heart felt thanks. Just a side note. I was installing the tank. I used a floor jack and lifted it in place. It is a very snug fit. I got under the car to put the new cross member in place and looked at the front jack stands. I could see air between them and the car. The tank was holding up the car - and without so much as a sound.
I can design and build a tank - take lots of pictures but can't figure out how in the heck to post them. I tried to use pip and couldn't begin to understand the computese necessary to post a pic. If you want pics - you will need to walk me through the procedure step by step.
There are a ton of free utilities for this. Google "photo resizer" and you'll get a ton of hits. Or, PM me your email address and I can send you a zip file of the one I use, it's really simple and easy to use (I used it all the time to send digital photos that are "email friendly" in size, yet look good to view on a computer screen). Once you've got smaller jpg file sizes, then you can use the PIP application to post on the forum.
Either way, congrats - this is a major good thing if it becomes available.
Somebody has hacked Paul JK's account! There is no way in Hell he would agree to putting something on a Fiero that is not 100 percent factory made, or made with exactly the same material or design as the original. No way I tell you!
Where do I start. The tank doesn't have a drain plug. Use the return line to pump out gas using an old fuel pump. The concern for the effects of scraping and rubbing is handles with a abrasive resistant sheet placed in areas of contact. The tunnel isn't a flat or smooth surface and nothing can fit tight enough to cause a worry about condensation. The tank sits at the same height as the hose clamps for the AC and heater lines. My car is lowered and I have never snagged one of those. The tank is .060 304 stainless. It is 3 times thicker than the stock tank and many more times puncture resistant. Anyone familiar with stainless knows what a pain it is to work with because it's so much stronger than steel. I sent Fieroguru a bunch of pictures so you will be seeing them soon. I gave Joe some suggestions on building his tank and he wasn't very receptive. He has someone else build the tanks to his specs, guess anyone of you could do the same if you had some plans.
You are off to a good start, and I like what you are doing 100%! Some of us Fiero (or Fiero based builds) guys are going to need alternatives sometime down the road as the present supply of good tanks seem to be disappearing and very hard to find in really good shape. I have a decent stock unit I am starting with but plans for one such as yours would be very beneficial to us all!
Kevin
[This message has been edited by Lambo nut (edited 02-20-2014).]
It looks like it was built quite well. I would love to see some under side pics to show the bottom of the tank and the mods needed for the bat wings on the sides to fit the double firewall panel.
As I have looked at making a tank for my personal car. I had planned to use a wide press brake (good friends with large metal fab shop) and bend the bottom and sides from a single sheet, then make the top and ends with flanges on them so I could use lap joints for the vast majority of the seams and only a few butt welds. This method keep the majority of the welds off the bottom of the tank and may reduce some of the welded seams, but it requires a pretty large press brake. I was planning to use 16ga mild steel, but may now switch to stainless.
Great job increasing the volume of the tank by a significant amount!
[This message has been edited by fieroguru (edited 02-20-2014).]
The "bat wings" fit without modifying the frame/cross member. The tank fits tight up against the cross member. I did make an access hole to make it easier to attach the fill and vent hose. They can be attached without the access but it's really hard to do. I could have made the wings wider and the wings could have been a little longer but I just felt anything close to 18 gallons would be enough. I could have put more gas in the tank if I kept poring after the initial fuel kick back but that is never a good idea. The expansion air space needs to have air in it - not gas. If a person keeps slowly adding fuel, like topping off the tank, the check valve will leak enough to allow gas to fill the expansion space. A lot of this will be explained when I do a build thread.
In answer to the cat question: I built this tank for myself and not to fit everyone else's needs. I don't have a cat but don't think they would interfere with each other. A heat shield doesn't take long to make and stainless has a low thermo-conductivity rate. The expansion area, as you called it, someone else called it bat wings, isn't necessary. It adds 2.07 gallons. Without the extra volume of gas the dead air space could be reduced and you still have at least 17 useable gallons. So in that event it would fit any car.
Fieroguru you may want to give your layout a little more thought. The bottom can have a sharp bend - true but it's over 90 Degrees. You could bend one side but not the other. The top needs a .50 radius to match the curve of the tunnel. Yes, you could make flange weld joints but the top rear section would still need to be in two pieces to provide the depression for the tubes and wires. The majority of the time spent on this tank isn't the welding, it's the cutting and forming. The welding goes very quickly and butt welds are the easiest to make. The only welds saved are the short butt welds joining sections together. By the by, the tank is well over 4 feet without the rear bump out. You are going to spend a lot more money cutting 4 X 8 sheets lengthwise to get the size you need. Even if you could make the 2 over 90 degree bends so close together, you will find you can't bend a piece of stainless that long and get a sharp bend. Remember if you make your bends from the top, the bends are less than 90 degrees, make them from the bottom and they are more than 90 degrees. If you make the tank in 3 short sections as I have, and out of steel, a small brake would work fine. Not that I can't be wrong or that I shouldn't listen to other ideas but I've been doing exactly this sort of design work for over 50 years. I know a lot is left to the imagination because of my not having the build write up done. Little things like machining the parts to make a leak proof seal for the sending unit or the home made tool to flange the fill pipe so the hose will stay on. I believe my design is the most buildable and can be easily modified to make stock fitting tanks with about 15 or 16 gallons capacity. I needed at least 18 gallons but I could have made the tank bigger. If I cut down on the expansion area this tank holds 19.7 gallons. It's a little more complicated with the check valve in the vent line. If the gas level is up to the check valve, no air can escape to the expansion tank. I did move the check valve higher in the sending unit. Lots of little details. Thanks for you help and thoughts.
Does this tank sit flush with the bottom of the floor pan like the stock tank? It appears a great deal taller than a stock tank. How nice it would be to have 18+ gallons!
Edit to add: Very well thought out and crafted.
Ken
------------------ '88 Formula V6 '88 GT TPI V8
[This message has been edited by kennn (edited 02-21-2014).]
Originally posted by woodyhere: I had planned to use about the same amount of air expansion space as the factory tank. I lost my nerve for fear the expansion area wouldn't be enough and made it larger by 240 cubic inches then my original design.
The expansion volume for the '87's and '88's is a metal tank between the space frame and body just outboard of the battery, above and in front of the right rear wheel.
Fieroguru you may want to give your layout a little more thought. The bottom can have a sharp bend - true but it's over 90 Degrees. You could bend one side but not the other. The top needs a .50 radius to match the curve of the tunnel. Yes, you could make flange weld joints but the top rear section would still need to be in two pieces to provide the depression for the tubes and wires.
I have thought quite a bit about the tank and the actual fabrication process over the last several years, just never have had the time to build one yet.
The press brake I use can bend 1/4" mild steel 8' long, so bending 16ga the full tank length isn't any issue. First bend is an upward bend right down the bottom center of the tank (lengthwise), then bend the two sides at 90 degrees (the first bend allows room for you to bend both sides w/o the previous leg getting in the way), last go back to the center and remove the current bend and actually bend it down slightly so the bottom is a shallow "V". This will pull the sides that are 90 degree angle inward at the top (just like if they shallower than 90). Keeping the top section small with small flanges, you can better evaluate the actual fit in the top corners because you can see how they fit w/o the long sides in the way. As for the top, I also wasn't planning to make a recess for the lines (too much work for minimal gain), just leave a small gap for the lines and wires and save myself some work - like the stock tank did. All my cars are 88's and have the expansion tank on the passenger wheel well, so I don't need much of an air gap in the tank itself.
I also buy all my material in 4x8 sheets and have multiple fieros that need larger tanks, so I am not worried about material waste.
There are literally hundreds of ways you can custom fabricate the tanks and each has its compromises. My method tries to maximize the use of bent joints while reducing the needed weld lengths and keeping as many welds as possible as lap joints vs. butt weld joints to speed up the welding process and reduce the risk of burning through the joint while welding. I am not saying my method is better than yours, its just the method I chose to use given my access to equipment and fabrication/welding preferences.
[This message has been edited by fieroguru (edited 02-21-2014).]
Will, The 87 and 88 tanks, as well as the earlier ones, have an air space in the top of the tank as well as the so named expansion tank in the fender well. The fill vent height determines the pop off point when filling the tank with gas. The air space in the tank is necessary for the check valve in the vent line, which goes to the expansion tank, to not have raw gas enter it and end up in the expansion tank. Boy is that a run on sentence! The check valve is that thingy that is on the inside cap of the fuel sender assembly. The prior to 87 tanks have a check valve that sits deeper in the tank.
I am thinking about making some tanks. I have a former student of mine that has a laser and water jet cutting business. I'll have to do a little checking on stainless prices and check to see if he would be interested in making some parts for me. I enjoy the welding and don't mind the machining or forming.
The expansion volume for the '87's and '88's is a metal tank between the space frame and body just outboard of the battery, above and in front of the right rear wheel.
Will (And you alone please), what affects will removing this tank and plugging the line have on the engine/car?
I'm not really a fan of the tank. Seems like a lot to go through to add just 2 gallons, including more than tripling the weight. I think I would've gone for an aluminum auxiliary tank instead. Just my opinion, props for going out and doing it.
Originally posted by RobertGT: Will (And you alone please), what affects will removing this tank and plugging the line have on the engine/car?
I'm not really a fan of the tank. Seems like a lot to go through to add just 2 gallons, including more than tripling the weight. I think I would've gone for an aluminum auxiliary tank instead. Just my opinion, props for going out and doing it.
For what its worth, my 88 does not even have this tank anymore. Part of Archie's V8 swap is to remove the tank. I have the gas tank venting into the charcoal canister. And I know everyone says "it will create a gas smell" they are full of crap. Its been over 3 years since the swap, and I have never smelled gas from the canister.
Robert the tank holds 18.7 gallons. What's with the 2 extra gallon statement you made. The 2 .07 gallon part was for the rectangular part added to the back. Why do you think Pontiac would put an expansion tank on the car if it didn't need it? You seem to read and believe what you want. Don't let the facts confuse you. The tanks are a lot of work to make. The materials are expensive. if I do make them It sure won't be a Walmart item. You get what you pay for.
Originally posted by qwikgta: For what its worth, my 88 does not even have this tank anymore. Part of Archie's V8 swap is to remove the tank.
You will be fine. The air gap in the stock 88 tank is more than sufficient to allow for a 100 degree temperature change in the fuel without pushing gas out the vent tube. I did the math back in 2008 during my 4.3 CPI swap:
quote
Originally posted by fieroguru: Fuel expands/contracts with changes in temperature and it is important to ensure there is enough room in the tank for it to expand or it could push fuel into the expansion canister. Gasoline expands at a rate of 0.00069 per degree F. So a 100 degree change in temperature with a 12 gallon tank will require .828 gallons of additional space. Expecting a 100 degree change is probably extreme, but it provides a since of scale.
Since my car is an 88, it has an external expansion tank on the upper passenger frame rail (I never measured it, but it might be .5 gallon). The top of the fuel fill vent tube is about 3" from the top of the tank. This creates an air pocket about 3" x 7" x 20" which is room for about 1.8 gallons of fuel (1 gallon more than needed for a 100 degree change - and assuming there was no secondary expansion tank).
On the 87/88 larger tanks (never tore the 84-86 vent system apart), there is a check ball in the vent line, but it isn't spring loaded. It just sits below an inverted funnel shape, so when the car finds itself on its top, the gravity will move the ball to the center of the funnel and block the flow of fuel. Since it isn't spring loaded, if you do push fuel to the expansion tank, gravity will bring it back into the tank as the volume is decreased. The only moderate concern here is to keep the vent line with a downhill path back to the tank so all the fuel can dump back into the tank and not sit and puddle in the vent tube.
quote
Originally posted by woodyhere: Why do you think Pontiac would put an expansion tank on the car if it didn't need it? You seem to read and believe what you want. Don't let the facts confuse you.
GM builds millions of cars that end up going world wide. They have to factor into their design any possible environmental condition the cars will be subjected to (temperature extremes), potential loss of capacity due to denting the bottom of the tank (especially given the Fiero tank's proximity to the ground), as well as factor in that some people will do some really stupid stuff, like forcing as much fuel into the tank as possible. If you do the math (like I did above) then you will see that the 88 fuel tanks have more than enough air gap to accommodate a 100 degree change in fuel temp, without the expansion tank, but it would be nearly impossible to see that condition in the US.
[This message has been edited by fieroguru (edited 02-22-2014).]
The only time I realized I needed an expansion tank was after I put the V8 in. I had pinched off the vacuum line to have one less line. With the tank freshly filled and accelerating hard, I could smell gas after I got home and parked the car in the garage. Never happened when I had the wimpy V6.
The check valve, which I also took apart, is for gas splashing up against it. There are several different designs of check valves used in the Fieros over the years. I don't really care if you guys use the vent line or not. I'm going to as long as it's there. It has no negative effect on anything.
Your negative comments, however have. I'm not going to make tanks or share plans. All you bench builders can make your own. I am happy to have an 18.7 gallon tank without the hassle of building more. All this BS for a line that you could have simply decided to plug. So, what have you accomplished trying to prove that you, who have never built a tank, know more about it than me?
The only time I realized I needed an expansion tank was after I put the V8 in. I had pinched off the vacuum line to have one less line. With the tank freshly filled and accelerating hard, I could smell gas after I got home and parked the car in the garage. Never happened when I had the wimpy V6.
The check valve, which I also took apart, is for gas splashing up against it. There are several different designs of check valves used in the Fieros over the years. I don't really care if you guys use the vent line or not. I'm going to as long as it's there. It has no negative effect on anything.
Your negative comments, however have. I'm not going to make tanks or share plans. All you bench builders can make your own. I am happy to have an 18.7 gallon tank without the hassle of building more. All this BS for a line that you could have simply decided to plug. So, what have you accomplished trying to prove that you, who have never built a tank, know more about it than me?
I am not sure who you are directing this negativity towards, but hope you haven't taken my contributions in this thread as being critical or negative. My posts were only meant to be accurate, informative, and helpful to those who read the thread.
If the day comes where I need to replace my gas tank I will probably have one built by Rick's Tanks in Texas. They are made of 304 stainless, and although they are expensive it would be a one time investment.
Is gas tank replacement a common maintenance item for you? Personally I'll go to the junkyard, spend $20, and get another gas tank that will outlast me assuming I don't go to Moab in my Fiero.
I think you did a great job and my biggest complaint is the 10 gallon tank of which doesn't really seem to hold 10 gallons. I like the pink foam mockup as well, very clever!
[This message has been edited by BrittB (edited 02-23-2014).]
For what it's worth, I only see one person negatively criticizing the tank (and it's not fieroguru). I think I speak for the majority of us when I say that the work you've done and shared is greatly appreciated and certainly is a major positive contribution to the forum. Disregard the self-appointed armchair judges.
For what it's worth, I only see one person negatively criticizing the tank (and it's not fieroguru). I think I speak for the majority of us when I say that the work you've done and shared is greatly appreciated and certainly is a major positive contribution to the forum. Disregard the self-appointed armchair judges.
What I find interesting is only one person said anything negative. fieroguru just offered alot of technical information as well alternative methods of production. What is even more interesting is how woodyhere went off because of one negative post and some advice/criticism. But just a few weeks ago, woodyhere was criticizing another member's proven work, who actually sells these, Here Pretty Ridiculous.
What I find interesting is only one person said anything negative. fieroguru just offered alot of technical information as well alternative methods of production. What is even more interesting is how woodyhere went off because of one negative post and some advice/criticism. But just a few weeks ago, woodyhere was criticizing another member's proven work, who actually sells these, Here Pretty Ridiculous.
I have to agree with you, the whole thing seems odd given his attitude and low post count, seems like a fast way to make his ratings bar pop up, and he won't like the results. The sad part, I like his tank, but as far as I can tell, he's just teasing us, I'm not sure he was ever serious about selling them.
For what it's worth, I only see one person negatively criticizing the tank (and it's not fieroguru). I think I speak for the majority of us when I say that the work you've done and shared is greatly appreciated and certainly is a major positive contribution to the forum. Disregard the self-appointed armchair judges.
