My 5.3 was pretty stout at 12lbs and made good mpg around 17-20 when I wasn't in it. I had the aluminum lc9 flex fuel vvt 5.3. I ran the magnum BB t72 turbo on it with a .96 a/r and spool was damn near instant with the 6l80 and 3.08 gears.

 

Did your lc9 have dod and vvt? What did you rev it to?

 

why aluminum block??? how much weight difference are you gaining vs losing strength???
ive always been told the major killer of the "borderline too much" engine is block flex and you should be flexing the aluminum alot more than you would the iron twin...

 

These blocks are some of the strongest blocks in the world. I'm not worried about block flex or a weak block. Not even an issue at all with the LS series engines. It is replacing an all aluminum engine and I don't want to add 100 pounds for no reason at all. For some reason people think that I the iron block is stronger, it is not. Hundreds of people, and I am one of them, have pushed these aluminum blocks over 1000 hp and have never had an issue. Some have pushed them over 1500 hp and have never had an issue.

It's funny how the original iron SBC engines both Chevy and ford made couldn't even handle 1000hp reliably. Technology and design engineering made leaps and bounds back in 1997 when they started the LS production run. I love it!