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Posts Tagged ‘gas tanks’

Early Gas Tank Danger

Thursday, February 11th, 2010

On most all early GM trucks their fuel line exited on the bottom of the tank. It was usually attached to a brass shut-off valve which threaded into the tank. In case of fuel pump or line repair, a person had to lay under the truck to turn the tank valve and stop fuel flow.

No doubt, this design resulted in many building fires as the trucks aged. By design, the tank is above the fuel pump. Thus, an un-noticed fuel drip or worse will continue until the tank is drained by gravity. What a dangerous mix in the many homes at that time with basement garages and nearby gas fired water heaters or furnaces.

In 1954 the needed change occurred. The gas pick-up line now leaves the tank on the top but extends down to almost the bottom. In this way, the gasoline does not drain due to a line leak and sediment stays in the tank bottom.

For the perfectionist wanting his truck authentic, the original system does not have to be a fire hazard. Regularly check the short neoprene flex line between the tank and fuel pump. There is a limit on how long the non-metal flex fuel line can last.

For the non-perfectionist: Use a 1954 gas sending unit in the 1949-53 behind the seat gas tank. With a few line alterations fuel can no longer drip from a neoprene hose between the tank and the fuel pump. That is “peace of mind”.

early gas tank danger 1

1954 and newer (above)

1953 and older (above)

1947-1948 Underbed Gas Tank

Thursday, February 11th, 2010

Among the many updates in the new Advance Design body style in 1947, one that certainly stands out, is the change in gas tank positioning. For the first time since 1936 it was placed outside the cab and under the bed.

The dimensions of this 16 gallon tank were based on the limited space between the right frame-rail and the torque tube drive shaft. It was very close to the wood bottom pickup bed and extended over six inches below the actual frame rail.

GM used this type gas tank in pickups during mid 1947 and 1948. For assumed reasons explained in an adjacent article on this website, it was placed back in the cab 1949.

This less than two year tank on the pickup (It was even a different shape between 1/2 and 3/4 ton trucks) has become very difficult to find in recent years, so the 1/2 ton was perfectly reproduced in 2008. Restorers no longer have to accept the high priced “just close” stainless 1/2 ton tank usually accepted by the rat rod enthusiasts.

These 1/2 ton gas tanks have recently been reproduced to exact original specifications. They even have inside an outside zinc plating. Check with Jim Carter Truck Parts, Part# MEG149.
Dimensions are: length 24″, width 12 1/2″, and depth 13″.

This gas tank is the same as the 1/2 ton “Single Unit” body trucks (Suburban, panel, and canopy express) during all the Advance Design years, 1947 through early 1955. With the 3/4 ton the truck has a longer frame so its gas tank could be longer and thus thinner yet it held the same fuel volume. it is important to realize this less depth allowed the tank to be higher above the ground. Therefore, it eliminated most tank contact with “high center” road rocks on dirt roads as with the 1/2 tons. To date, the 3/4 ton gas tanks are not being reproduced!

underbed gas tank 1

Bottom View (above) 1/2 ton

underbed gas tank 2

Top Left View (above) 1/2 ton

underbed gas tank 3

Top Right View (above) 1/2 ton

underbed gas tank 4

Outside View (above) Without Grommet

underbed gas tank 4

3/4 ton tank longer and thinner with same capacity

1937 – 1972 In Cab Gas Tank – Friend or Foe

Thursday, February 11th, 2010

What’s this bad rap some people give the GM pickups with in-cab gas tanks? For 35 years GM protected these tanks from collisions by double wall reinforced cab metal, doors, and seat frames. The 1937-46 pickups even secured the tank under the seat and surrounded it on three sides by the welded to floor heavy metal seat riser.

If you and your truck are ever involved in a collision so major that the gas tank begins leaking, then imagine what could be occurring if the tank was in most other places on the truck. Unless you have found a narrow tank that fits inside the frame rail and away from the drive shaft, you haven’t located a safer location than what GM used between 1937 and 1972.

For approximately 18 months, beginning with the 1947, Advance Design body style, GM placed their pickup gas tanks under the bed inside the frame rail. This location, while protected from side impacts, was very susceptible to damage from road debris. Leaks from being hit by rocks and stumps soon caused GM to again place the tanks in the cab. Possibly, a protective panel would have given the tank a shield but GM did not use this option. The tank went back in the cab.

In these older trucks you instantly smelled gasoline if the sending unit gasket or gas filler hose began to fail. Trucks with under the bed tanks usually must be parked and dripping before a person smells the vapors.

Important:  If you critique the early in-cab GM gas tanks, don’t forget what General Motors did to the truck series beginning in 1973. Can you believe? They secured the tank in their pickups to the outside of the frame rail under the bed. The only separation from a broadside accident is the single layered sheet metal bedside! It doesn’t take much of a side impact to flatten the tank with disastrous results.

SAFETY FIRST! GM had the right idea! This tank is protected by the original heavy steel seat riser surrounding it and then it sits within a double layer metal cab. Compare this with some people’s idea of hanging their gas tank behind the rear axle with very little protection from a rear end hit.

REMEMBER: the Ford Pinto that was rear-ended in the 1970’s burst into flames  and the 2 Pinto passengers were killed?  Yes, it came with a factory issued rear mounted gas tank! Check out this story on a Google search…

Don’t make your truck more dangerous than it was originally!!

in cab gas tank 1

This photo shows an in cab underseat gas tank as used between 1937 -1946…It lays inside a heavy gauge metal seat riser as well as being inside of a heavy guage double layer metal cab. (above)

in cab gas tank 2

The above photo was taken of a 1952 Chevrolet 1/2 ton daily driven pickup. The owner was so concerned about the gas tank in the cab that he placed it under the bed behind the rear axle. The non metal tank is just waiting for a rear end hit at about 20 miles per hour. The original bumper will offer little protection and the contents of the tank will fly in all directions…Is this a moving bomb ready to explode?