By John Gunnell
There are a number of approaches to take when restoring the gas tank on a collector car. The easiest is to get by with the old tank, hoping it won't leak and that the rust accumulation inside will be cleaned up once you start running gas through it. Sometimes this works, but as they say, "Good luck with that."
If the problems with the tank amount to little more than minor cosmetics — such as a few shallow dents — a professional shop may be able to (carefully) weld or glue "pull rods" to it and pull out the dents. These shops usually work on both gas tank and radiator repairs and will be listed in the local telephone book.
If the gas tank is very rusty inside, there are acid solutions that can be poured into it, sloshed around and poured out again. The tank can then be rinsed and if still rusty, it can be treated the same way over and over again until clean.
Another option is finding a good used tank on a parts car or a salvage yard car. Of course, this is not nearly as easy in 2015 as it was years ago. The increasing prices that salvage yard owners can get for steel have reduced their desire to hold onto to older cars. Also, most tanks in salvage yards are rusty.
A fourth possibility exists if you have a cult car — such as a Corvette, Camaro, Mustang, Nova, Tri-Five Chevy, etc. Then, you can order a reproduction gas tank from a mail order catalog. The number of reproductions available seems to be growing each year. And if total originality isn't a big concern, there are numerous suppliers of high-quality tanks that can be adapted to almost any car.
None of these approaches applied to an early postwar Mopar we were working on. The car was a rare body style. We believe that only 76 like it were built between 1946 and 1948. It had a straight eight engine and a gas tank with a large dent in it. Reproduction gas tanks were available for the six-cylinder edition of this car, but the larger gas tank for eight-cylinder models was not available. While the reproduction tank for the six-cylinder model would probably work fine, the owner wanted the car to be totally original with the larger eight-cylinder tank.
The top side of the original 1948 Mopar gas tank doesn't look bad at all.
It was the bottom of the tank that took a real beating over the years. The metal is fairly heavy sheet and the dents could not be removed by using wooden rods through the inlet or welding on dent pull-out sticks.
Here is a close up of the damage on the underside of the gas tank.
We first took the tank to a professional shop that worked on radiators and fuel tanks. The technicians there carefully evacuated all gasoline fumes from the tank, then tried to pound out the dent by pounding on wooden sticks inserted through the tank's inlet. Since the dent could not be removed this way, the shop workers then welded rods onto the gas tank's outer surface and tried to pull the dent out. This did some good, but the dent was big and deep and still remained.
Internal rust was a secondary problem. We had already tried fixing a rusty Triumph tank using an acid kit and had less than great results. The procedure was hard to do in Wisconsin in the winter as it required repeated rinse outs with water. Our garden hoses were already put away for the winter and we were not keen on bringing a gas tank into the house. The small Triumph tank had been cumbersome enough and we couldn't imagine filling the Chrysler tank with liquid and trying to slosh the solution around to get it on all of the rusty areas.
It was clear that the only way to repair this tank was to cut it open, fix it using standard sheet metal repair procedures, treat the rust while it was cut apart and weld the halves back together again. Since cutting into a metal gas tank is dangerous (even if you think all gas fumes have been removed) we started looking for a shop willing to attempt such a repair. Although there are plenty of gas tank repair services that advertise in hobby publications and on the Internet, we couldn't find one that was willing to cut the tank apart to make a nice repair.