What's the biggest size I can make the 4.8 go I heard the biggest is a 383 or so. I also have a ls1 bloc. Don't know weather to build the ls1 block or sell it and build up the 4.8. What can I do to the 4.8 come on guys help me out

 

Both blocks will use the same cranks and should be able to be bored to around 3.903 so they have the same potential for cubic inches. I think that a few companies make 4.125" or 4.2" stroke cranks which could get you in the 390+ cu in range. However, with that long of a stroke, you a pushing the limits with piston compression height, rod ratio, etc.

 

I wouldn't build a 4.8 LS past 5.7 if you want it to run past 150,000 miles. The 408's from what I read can be a bit notorious for killing rings past a 100,000 miles. The deck height is not sufficent to prevent piston rock which in turn kills the bore then rings, but it will be one hell of a motor for those miles.

I am looking at this 05 CCSB 1500 with a 130,000 miles for myself, and if I decide this is the one. I will swap in a 6.0 with a cam, tuning, and full exhaust . It should be close enough to 400 crank hp, and meet CA smog, but I will do the swap after I get all the other bolt-ons in place or the motor gives.

Or if you have a few more dollars a 6.0 or 6.2 with L-92 heads, and a good cam can get close to 500 crank hp CA smog passable. Or build a LS 421 it just comes down to your ability to swipe the card and tolerate motors that don't last that long, but with insane power it may be worth it.