I was thinking, instead of going the 6.0L route like everyone else, that I could pick up a 4.8/5.3 much cheaper. Rebuild the bottom end with forged rods and pistons and bump the compression to 10.5:1-10.8:1 and get cam. And maybe just upgrade the heads later. What is everyones opinion on this? And how much RWHP do you think it would yield?

 

It doesnt make any sense, forged internals will cost you more than a 6.0 and then you would be lucky to get rwp of a 6.0,

no replacement for displacement

 

I agree just run the higher compression of the 6.0. instead of getting forged internals.

 

You will find most folks lean towards the 6.0L swap. I did something different, got 350/380 rwhp/tq out of it, for about $3000. Granted this was doing everything myself so if you are not build capable the cost would approach $4000. You are then in 6.0L territory cost wise. I also used a 01 Z06 cam to stay emission legal, a healthier stick would have easily put it over 400/400.
I enjoyed the build and the bragging rights, all depends on what your wallet and schedule will allow. You are right on tho, a used 4.8/5.3 motor can be had for less than $500 shipped if you look hard enough.

 

Well what would you guy suggest? I just got 20"s put on with 275/55s and this truck feels slower than ever. I need some power back. Maybe gears or torque converter (3200). Something needs to be done quickly.

P.S. Will my gas mileage get worse with these tires? They're taller than the 17s too...

 

You will probably get worse mileage due to the heavier tire/wheel combo. Unless you went with forged wheels you added a ton of "unsprung" weight to the drivetrain.
Gears will definitely get some of your lost power back, a TC will help you rev faster but not add any power. Do the gears now and the TC if/when the motor work happens.

 

if i remember correctly didn't CHP or CC do a write up on these blocks and it said the 5.3 block could be safely bored to 4"? help me out here guys. if you did grab a 5.3 block you could easily have the cylinder walls sonic tested to see how far you could take it. if it would support a 4" bore, combine that with the stroke of the stock crank and you have 367cu/in. throw a 4" crank and you have a 402cu/in beast.

 

i have only read a few posts where others have turned a 5.3 in to 383 ci motor. have not read if any one has gone larger like 408 or more on a 5.3.

 

i know it may depend on the year of the 5.3, but here is a thought.
i know the 5.3 runs the same crank and rods as the 6.0, the strongest set would be the LQ9 6.0.
how much stronger would the LQ9's crank and rods make the bottom end of a 5.3?
some on here and ls1 tech are seeing 500+ on this stock crank and rods.

 

The crank and rods are identical on the 5.3 and 6.0L motors, same part numbers. I verified this when I made my 383ci stroker from the 5.3 iron engine.
The max bore on the 5.3/4.8 block ( same bore size FYI ) is 3.905" and is what I bored it out to. I did a sonic check pre-post and the thinnest post area was 0.157" ( usual min thickness is 0.150" ). So, going the extra 0.100" or so for the 4" bore would be very dangerous IMHO. You could sleeve it but then are into the machine shop for some serious coin.