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Corvette Gas Tanks - Let's Get Tanked
Replacing your '63-'82 Gas Tank in one day
Apr 10, 2007
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Corvette Gas Tanks - Let's Get Tanked
There's more reason now than ever to protect your petrol.
Extensive rust is evident on the exterior surface of this New Hampshire Corvette gas tank. Tanks are unpainted and the thin, plated coating is fairly fragile. Tanks can also rust-through from the inside out when trapped moisture accelerates the corrosion.
With the body-off, it's easy to see how the front of the tank rests on a removable crossbar support. Removing the crossbar enables the front of the tank to rotate down and allows the tank to drop out from below.
The rear framerail supports the rear of the tank. Although this is a custom frame featuring a late-model suspension for C2s and C3s, the tank-mounting location is the same as on an original frame.
The tank is one of Corvette's bigger parts, but it still can be shipped to your door. Quanta includes the filler neck gasket, filler neck screws, sending unit rubber gasket, and lock ring with each new tank.
The antisqueak strips are likely to need replacement, and a pair only costs $5. If your hold-down straps are rusted, a new set can be purchased for $40.
The gas tank sending unit has an internal coil of resistance wire that can eventually break due to wear from the slider. consider replacing the unit even if it is not rusted. The failed sending units I've dissected usually wore out at the quarter-tank level. I'd surmise the owners didn't like to fill their tanks. And that was when a gallon of gas cost only...oh, never mind.
The sending unit is held in place in the tank by a lock ring; a rubber seal goes between it and the tank. The fuel strainer comes with the sending unit, but it can also be ordered separately if the sending unit is not being replaced.
Parts located on the top of the tank include the overflow boot, nipple, drain hose, hose spring, and tie-down straps, available together in an Overflow Kit. The purpose of these parts is to drain any gas overflow to the ground during a fill-up, to avoid the exhaust, spare tire carrier, and other parts. The remaining top end parts are the filler neck gasket, screws with o-rings, and gas cap.
After draining the gas tank, remove the spare tire carrier and cover. Use caution when removing the long front bolts; you don't want to break loose their weld nuts inside the frame. A forthcoming article will detail restoration and replacement of these parts.
Slide the clamps out of the way, and then carefully break the hoses loose. If the hoses are being replaced, slit them longitudinally to ease removal. Wear safety goggles and keep your head away when removing the hoses to prevent gas getting into your eyes.
If there's a fuel-vapor separator on your tank, it's located on the top left side. Although it is a challenge to see or reach, treat it gently, especially when removing the hoses. If the separator is original, the plastic will be brittle, and replacements can be hard to find.
Oil the exposed threads and remove the bolt from each hold-down strap. There's no need to worry about the tank falling; it is still supported by the crossbar. While you're there, inspect the framerails for surface rust. When the tank's out, it's an opportune time to brush on the POR-15 rust preventative paint.
Remove the four bolts that attach the tank crossbar to the frame. A 9/16-inch box wrench can be slid inside the frame to hold the bolt head. Leave one bolt on each side connected by a thread, support the tank by hand (it's light when empty), and finish removing the crossbar. Lower the front side to remove the tank.
Two tabs determine the alignment of the sender in the tank. Press the sender against the rubber gasket and engage the lock ring by hand. Then use a punch or screwdriver to slowly tap the cam lock ring around until it is fully seated.
The threaded holes for the filler neck screws open into the tank, so make sure the o-rings are in good shape on each screw. To the left of the filler opening is a pressure-relief valve. This particular one took a while to seat properly.
There's nothing tricky about the installation; it's just the same steps in reverse order. However, before tightening the hold-down straps, check the position of the antisqueak strips between the tank and crossbar or frame, and check that the tank is centered in the frame.
Some areas of this tank are completely rust-free, while other areas are heavily rusted. This is common when the plated lead barrier coating of Terne steel begins to deteriorate. The filler hole is considerably larger on this '77 tank to permit insertion of the rubber bladder.
The '75 Corvette model year introduced a gas tank with a reinforced rubber bladder to reduce the chance of gas leakage after collisions that damaged the tank. An added benefit is that as long as the bladder is in good shape, rust perforation of the tank won't cause a leak.
If your tank is original, there may still be a buildsheet (tank sticker) glued to the top surface. That's another reason for removing the tank-to preserve the sheet, which lists the options the car was built with. Photograph the sticker before attempting to separate it from the tank. These scraps were all that was left of mine.
Attach about eight feet of transparent 1/4-inch rubber hose to a 1/4-inch brake line that's 12 inches or longer. The clear hose makes it easy to see, and, therefore, not taste the gas when starting the siphon. The 1/4-inch diameter produces a convenient slow rate of flow.
Insert the tube into the tank and position it in the front of one of the recesses at its lowest point. A strong flashlight helps, but you can also feel when the tube slides down into the recessed areas.
Start the siphon to vacuum the water and dirt from the tank. Tip: bump the car slightly to cause the gas to move; this helps to see the edges of the water puddles beneath the gasoline.
A few minutes of gas tank maintenance can prevent future problems by removing water and dirt visible at the bottom of the container. The siphoned gas can be salvaged by pouring as much of it as possible into a second, clean container. If no dirt or water was transferred to the second container, this gas can go back into the tank.
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