Aluminum does well or else GM would not build engines with it. There are many guys running mega HP engines using the aluminum blocks. The 6.2L block is aluminum. The only reason to really go with cast iron is expense and the ability to bore the cylinders oversize. Until GM came out with the L92 engine it was cheaper to buy the cast iron blocks for the lsx based engine buildups. It is still cheaper to go with the cast iron engine but I know if I had the money and were to do it all again I would buy an L92 block and stroke it. Saving 100 lbs on the weight of the vehicle is going to save you fuel and reduce your 1/4 mile times by .1 so why intentionally slow yourself down with a steel slug when you can have light weight aluminum. My old LS1 block and LS6 heads are off at the machine shop getting redone. That is how much faith I have in those parts. The only bad part about the aluminum block is the cylinders can't really be rebored.
If you honestly think that steel is so much more superior to aluminum for performance, get rid of your aluminum heads and switch over to the cast iron Gen3 heads.

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