Why would anybody fill an aluminum block - seems counter productive and a waste of time - I see no gain to be had. If you want a solid block (no water jacket) order one
Because an aluminum block will move around some. My INDY block is now half filled with Rock Block. It was mainly done to help stiffen the block up, as it was previously damaged. I was told an aluminum block will not pull vacuum like a iron block, but I was able to pull a steady 10lbs, at idle, and went over 20 before adjusting the relief valve.
....How is that block holding up for you? And at what power level?