There's no need to heat to a high temperature. If you're careful just heating the cylinder up slowly in an ordinary domestic oven will be fine (Oh it's so wonderful being the lady of the house). It's trying to bend the fins on a cold alloy casting that will mostly result in failure. Ease the fins gently, use smooth jaw pliers and it's useful to have them hot too. Oven mitts are the kitchen bench engine mechanic's best friend.
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