Limits of a stock LS1 block
Limits of a stock LS1 block 
I remember back in the day QMP/LS1Motorsports took a bone stock high mile motor, bolted on a turbo, and made ~750 at the wheels, and couldn't break it.
I also believe Harlan was running a stock block and running 8s at about 1200hp while boosted. This was before the age of aftermarket blocks of course.
If you're planning to hit 4-figure horsepower land though, most people would go with an iron block or an aftermarket GMPP LSX or World Warhawk block. If you're going to spend that much money making power, makes sense to leave the stock LSx block at home. Plus less worry about lifting the heads with a 6 bolt block.
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
I think that tuning is more important then block selection when talking about the physical limits of such. I have seen several cracked sleeves in the 400 hp range 
