I have had a lot of trouble with the aluminum blocks. I prefer the cast iron ones. Bores can be held tighter, and rounder......Feels like its making more hp, but its heavier.

Besides the sleeves leaking coolant every where,. I think in some of the aluminum blocks there is not enough material behind the sleeves to keep it round during boring and honing. I think if your going to go aluminum, you want nice thick sleeves, and you want nice support behind it. Keep the bores smaller, and put your own sleeves in....