Since we have a boring bar I will most often just bore them till thin, and then lift the remnants out. Heating the block in an oven will "often" work, but I have had instances where the interference fitment was great enough that this process just didn't work as well as one might have hope for. And then yes, I have utilized the "torch", but in doing so I will usually utilize the TIG torch without any rod, heating the sleeve wall surface just to the point of transition, just to the point of where you would typically begin to lay some filler material, but then move along rather quickly (lots of amps) as the intent is not to cause excessive heating of the aluminum, drawing a line from the bottom to the top. I will make two vertical passes 180 degrees from one another, allow to cool and the sleeves "will" fall-out.
But do note that once you decide to use the "torch", your committed, you can't get cold feet partway though the process and then expect the machine shop to be happy about your request to now bore them out!
Scott.
