What would happen if i added oxygen into my pencil torch.

Ok I know its probably a bad idea, but my friend and I were talking and got to wondering if we filled the torch with a little oxygen on top of the butane what would the results be? im thinking no flame(bad airfuel mixture), he is thinking BOOOM.

You would have a heck of a time getting oxygen inside there, since you can't liquidfy it . And your friend is right, is you did get oxygen inside there, you would have the components required to make a bomb. You would have a contained oxygen source and a fuel. It would probably blow the chamber apart. This is what is going on inside of a internal combustion motor where the fuel and air are mixed and contained. And this is a significant explosion when a spark is introduced

In a oxy-acetylene torch they mix the gas only right at the exit point of the tip of the flame. Plus the oxygen pushes up behind the gas. Oxygen can't burn without a fuel, so there is no chance of the flame going down the tubes on a oxy-acetylene torch