To my knowledge...you cannot sleeve one.
Just looking at one in front of you...you would immediately 'see' the problem. The aluminum isnt thick to start with.
That's why filling and maybe some wax to make internal channels to cool some.
Most of the heat is up at the top and the Chamber anyways so it's like the last inch or two of the cylinder that really needs water and unfortunately that will have to be filled. Chicken wire, block fill and some candle wax or something to melt out and leave a coolant passage around the cyls
