going to build a 4" stroked lg9 6.0 for a ump modified. My ? is how much hp can this block handle.

 

I'm sure it can take whatever you will throw at it. I would say at least 1000hp...if built correctly. If you meant left stock internals, I'm sure it will be like every other LS motor for the most part and be good to 500-500 rwhp....

I'm sure someone more knowledgeable will reply and let you know for sure

 

LQ9 fwiw

Built properly, it'll be good for huge hp numbers. Over 1000hp...

 

Iron block will probably take anything you can throw at it.

 

Might wanna take a look at this. Only mods done were ls6 cam and springs/retainers & turbo kit.
STOCK LQ9 (bottomend/heads) does 825hp/875tq on 19psi
**dyno video**
http://videos.streetfire.net/video/D...ker_172501.htm
1/4 pass
http://videos.streetfire.net/video/D...9-1a56a5d023f5

Thread:
https://ls1tech.com/forums/multimedi...5hp-875tq.html

 

I'm pretty sure Kurt and W2W made over 2000hp with one, but don't expect to see that on the stock caps or without hardblok. Probably o-rings too.

 

great to here. seeing some of these advertisments of new blocks good up to 500 hp had me worried. im going to put these blocks thru 25 maybe 30 min.of hell. hoping for 650-700 hp. so i wanted to make shure i was starting with a good foundation. if anyone could think of something that i should do to the block to help it handle all this punishment i would be greatfull.

 

ARP hardware and good machine work and it should be fine. You could look into O-ringing the deck or replacing the factory powdered metal caps with some nice billet ones but it gets expensive from there.