Ricardo, I guess I'm stupid but what do you mean by a neutral flame ?? I've used a torch for a long time and never heard of it.
Not stupid at all. Perhaps you know what I'm taking about by another name!
I first learned to work with metal in the early 60's. When gas welding or cutting with Oxy/Acet, I was shown how to open the gas valve first, but to also add a small amount of oxygen when igniting the flame.
This prevented acetylene soot, and also initiated a real flame.
Once the flame was going and with oxygen, you can see distinct feathers from and created by the oxygen.
As you increase the oxygen the two feathers will blend into one.
That is what I learned to be a "neutral" flame! (I. E., the hottest flame per acetylene)
Any less or more oxygen, the flame will cool some.
Too much oxygen, and your flame won't be correct while cutting...... and you'll fight oxidation while gas welding.
But back on topic.......
I think that unless you are extremely careful, Oxy/Acet is a bit too hot to use for heating and expanding an aluminum drive case!
If Mapp Gas won't do it, you likely have some severe corrosion issues.
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