What is most horsepower the ls1 can handle? Also when it would give out, is it because of the rods and pistons or is it because the block itself? Just looking to get an idea of what they things can handle?

 

The pistons, rods, and rod bolts, are the weak links. There are guys here making 1000hp on ls1 blocks and cranks. My engine has a stock crank with forged rods and pistons with arp rod bolts and I'm shooting for 600rwhp, I'm not worried about it one bit.