A 1930 s triumph tank was brought into the workshop with the customer saying he cannot find anyone to restore it to it’s original fuel capacity. The problem being it had been “Petsealed” 30 years ago and the modern fuels containing ethanol were attaching the old style sealant, thus causing a lot of problems.
The first thing to do was to cut the underneath of the tank without generating any heat or dust due to the carcinogenic nature of the ‘Petseal’. This was done by employing the shallow drilling process. First an opening is planned under the tank and scribed out. Then a chain of holes are drilled each just breaking into each other. It is important to wear a respirator for this sort of work.
When this is done the flaps that have been created are opened up or removed so as you can either get your hand in or get a tool in to remove the old ‘Petseal’.
In this case I made two apertures as small as possible so as not to disturb with welding heat, the original paintwork and chrome restoration that had been carried out several years before. What was inside the tank were sheets of ‘Petseal’ as thick as 1 inch. The way this was removed was by a long series drill poked through the apertures into the old ‘Petseal’, making sure it didn’t go right through to the inside of the petrol tank.
Old ‘Petseal’ can be readily fractured by drilling a hole partially into it. Then put a rod of steel into the hole that you have drilled and a pull in any direction. It will fracture it into manageable pieces depending what size inspection apertures you have chain drilled.
You can see what I have removed from inside the tank. The old type of ‘Petseal’ is known to react with ethanol in modern petrol’s forming a gummy residue. This had also blocked off the crossover tube and the petrol tap decreasing fuel flow to the carb.
After all of the ‘Petseal’ had been removed I brazed up the string of holes. The work that I carried out in no way disturbed the chrome plating or paint on the outside of the tank so saving the customer a complete restoration job.
The tank then has to be pressure tested. This will show up any pinholes in the brazing. Generally about 5lb psi will show any leaks with the aid of a cup of weak fairy liquid and water mix, this is brushed over the weld prior the painting. If there are any leaks they can either be brazed over or soft soldered.
When all is done the tank should be re-petsealed. The modern ‘Petseal’ is ethanol resistant and will prolong the life of the petrol tank.
Here are some other pictures of a variety of petrol tanks.
By Terry Ives