Moving the gas tank on a C3

SuperBuickGuy

SuperBuickGuy

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My trials, and now the trials of 69427 with their fuel system brings up the question.

Why would you ever leave that gas tank in its stock position? The tank is literally above the carburetor and in an accident, should the line be severed, would simply siphon all the fuel out of the tank. Not to mention that weight is actually the highest weight in the car and would always negatively affect handling.

framegastankpicture75corvette.jpg

So what am I missing? spare tire? I have a great system for that, it's called AAA - I call them, they haul me to a tire shop (this presuming my fix-a-flat and small, electric pump doesn't fix the problem)
 
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I guess placing the spare tire on top of the tank was not an option LOL ....

All cars came with spare tires until when ? 2000 or so ?? I would say that's the main reason the tank is where it is ... Lowering it seems to be a good idea though :)
 
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Putting it where the spare tire carrier might create more of a hazard for a rear end collision?

I think in a C6, the twin fuel tanks are located low, but are in front of the rear half axles. The fuel tanks are on either side of the transmission. The C6 tranny is in back and is mated directly to the diff. (BTW the C6 fuel tank and pump are unbelievably complicated! It has an electric pump, and two passive pumps known as a venturi pump and a siphon pump. All of the complications are to meet environment rules concerning gasoline vapors.)
 
I'm guessing a simple fuel cell would be the best option.... simply run the fill tube up to the normal fuel inlet - my fuel sender isn't working, so this thread may have a quick application.
 
Early C3's the fuel line comes out the bottom of the tank. Cut the line and it's going to drain the tank. Not a bad thing because there is always some head pressure at the pump. It is bad if the line gets cut.

Dropping the tank lower has to lower the CG. But will dropping the tank 6" lower cause enough change to make it worth the effort? Maybe on one that's not on the street, but I'd think that there are enough other things altered at that point it wouldn't be a gain. On the street where the chance of getting whacked in the azz end are somewhat greater, I'd think the option there would be a fuel cell.
 
Whats more dangerous. The fuel tanks on our C3's or the saddle tanks on my 85 flatbed,that are on the outside of the frame rails :amazed:
 
kwplot34 said:
Whats more dangerous. The fuel tanks on our C3's or the saddle tanks on my 85 flatbed,that are on the outside of the frame rails :amazed:
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Unless you strap a bottle rocket to the tank, no problem at all. Still, I think the CG will lower by 12" or even more (I'll put it where the spare tire was) - and at 7# per gallon/15 gallon tank, the weight is really pretty substantial - especially since the baffling that I've seen in those tanks is almost non-existant. Only down side of a cell is it takes longer to fill.
 
SuperBuickGuy said:
Still, I think the CG will lower by 12" or even more (I'll put it where the spare tire was) - and at 7# per gallon/15 gallon tank, the weight is really pretty substantial -
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Logic sounds good - and with a body off ought to be easy.
Opps- While-I'm-At-It.
Not really -- it was in the plan anyway. Honest!

Here is a calculator that might be helpful for other weight distribution moves:

http://www.baranidesign.com/weight_distribution/weight_distribution.html

Cheers - Jim
 
I've heard that the spare tire was actually part of the collision enegry absorbtion design. It needs to be there in case of getting rear ended. Any truth to that?
 
1976-red-corvette-n.jpg

vettewreck1.jpg
vettewreck2.jpg

by replacing the tank with a cell in the tire location, I expect it'll be as strong (if not stronger) then it would with the tire.... but none of those cars had a tire in them; so dunno - I'm pretty sure crash testing in the 70s didn't include rear ending.
 
You can install an 8 gal fuel cell and the filler lines up with the factory fuel door. A 10 gal will work too, just doesn't line up as well with the fuel door. I used the same bracket from the original tank.
 
I don't understand the point, gas weighs like a hair over 6lbs a gallon and even full you have what 130lbs of gas. But how often is that since the majority of the time its usually a 1/2 tank and that drops the weight to 60-70lbs. Sure it affects handling to some degree but I doubt as much as you think. I think if you baffled the tank you would benefit more that way then moving the tank or trying a fuel cell. As for fuel leaking from a busted line that is going to happen no matter what that gravity feed and it is highly doubtful you can ever change that. Better to install high pressure or stainless lines and not worry about it again

If it were me I would just deep sump the fuel tank and install a pickup down in the sump so you can easily run at near empty levels and still draw fuel. this way fuel neck mods and re-positioning of the tank are not necessary.

Basically how a oil pan is but a much larger version that say holds 4 gallons below the bottom of the current tank. Plus on long trip you have extra fuel capacity.
 
The point:
1) moving 130 lbs from well above the motor, to below it thus helping the CG
2) reducing the likelihood that the tank could siphon out if the line split
3) putting a more robust fuel tank in the place of the current tank (on that note, everyone gets all twitterpated about the tank below the rails being unsafe; yet it's the same level of unsafeness with it above the rails; maybe even more so since there is a large number of SUVs that would ride above the rails then under it)
4) being able to pass tech
5) I'm not welding on a used gas tank to put baffles in place or a sump
6) the possibility of greater capacity for long hauls
7) baffling for fuel injection
8) fixes the sender problem (my car)
9) Costs less to replace the tank then modify the existing one (especially since I'd have to hire someone with nothing to live for to weld on this tank). :)

But other than safety, aesthetics, and cost... nope, can't think of a reason why. Your turn Jeff - tell me why leave it where it's at
 
The later c3's have a tank bladder and a steel containment device. It is pretty heavy. My 75 had both. I think the containment thing was heavier than the tank.
 
JeffP1167 said:
I don't understand the point, gas weighs like a hair over 6lbs a gallon and even full you have what 130lbs of gas. But how often is that since the majority of the time its usually a 1/2 tank and that drops the weight to 60-70lbs. Sure it affects handling to some degree but I doubt as much as you think. I think if you baffled the tank you would benefit more that way then moving the tank or trying a fuel cell. As for fuel leaking from a busted line that is going to happen no matter what that gravity feed and it is highly doubtful you can ever change that. Better to install high pressure or stainless lines and not worry about it again

If it were me I would just deep sump the fuel tank and install a pickup down in the sump so you can easily run at near empty levels and still draw fuel. this way fuel neck mods and re-positioning of the tank are not necessary.

Basically how a oil pan is but a much larger version that say holds 4 gallons below the bottom of the current tank. Plus on long trip you have extra fuel capacity.
Click to expand...

Funny to hear you say that, because one of my bugs with the L98 FI on this car WAS the tendency of the engine to skip/STALL in a hard turn if the tank was below 1/4.......So at Harbor Freight, about 2 years ago, I noticed a 5 gallon portable air tank on clearance....20 bux....make me a offer I can't refuse....so to mod it for gasoline sump tank, so there it is under and forward of main tank all bolted into the old spare tire forward bolts and the handle bolted to the removable gas tank cross support....plumb it up and 5 gallons and no drop outs.....:bump:total cost maybe 30 bux......

:bump:
 
Those pics show some pretty bad rear end damage...and no fire... Moving that tank seems like alot of work for a DD to solve a problem that might not exist. And how much benefit to moving the CG, again for a DD doesn't seem the squeeze is worth the juice. On a track car, a different story.
 
baby's got a big back... that's a lot of tank

I love the removal of the bumperettes - that looks really good

I was under the car last night, and calculated that I could build a tank 18x38x8 and have a net volume of 23.6 gallons. That would nestle it between the frame rails, and by being shallow, it'd be easy to baffle (although, I'm considering foam rather then baffles) - and still behind the bumper.
 
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