I have a 2004 regular cab sierra that I plan on swapping motors in. I currently have 4.8 making 300 rwhp and would really like to get to 450 rwhp. Just bought the truck a month ago and not sure which motor to get. I know if I get the 6.0 all my bolt ons will swap over, but the power in the 6.2 is just ridiculous. Additionally, there's a gen 4 6.0 I can get for 1900 with 50k miles on it and a 6.2 LS3 out of a 2012 camaros SS i found for 4000 with only 1k miles. Just looking for some input on which way to go cause this will be my first motor swap. Thanks in advance.

 

If money is not a problem go with the 6.2. The 6.0 lq9 gen III everything from your 4.8 will bolt on to the lq9 plus all your wiring and pcm will work.

 

The wife is gonna complain no matter what. Both engines I'm looking at are gen 4, so I'm gonna have to by a wiring adapter. And if I go 6.2 I have to have motor mounts, just looking for someone that has been down the road to see how much the difference in install is money wise. Either way I go, I'm dropping new heads, cam, intake, headers and 102 mm throttle body. Hoping that will get me close to the 450 rwhp without having to charge or turbo it.

 

It would be less hassle to find a gen III motor. Otherwise you have to deal with a lot of stuff to switch over. Here is a previous post I made about a LS3:

You need to change to 24X crank reluctor or use an adapter box. Texas Speed offers conversion package that will include the LS2 timing cover with camshaft position sensor, LS2 valley cover, LS2 lifter trays, LS2-specific 1x timing set, and plug-n-play harness extensions for the camshaft position sensor and knock sensor.

Knock sensors need to be addressed. The best option seem to be using the Gen III knock sensors relocated to the side of the engine which requires drilling and tapping to fit (Use a hand drill and 8.5mm drill bit to open up the blind M8 female threaded bosses on each side of the lower block where the LS3 knock sensors normally mount or use any un-used M10 engine mount bolt holes.).

Cam can be a 3-bolt LS1/LS2 style cam. But, you need to use the appropriate timing set and timing cover.

That leaves the top end which depends on what heads are picked: cathedral or rectangle port. If LS3 heads are used, then will also need a L76 intake manifold, MAP sensor relocate and adapter, LS3 fuel rails, LS3 injectors with adapter harness, and cable drive throttle body.

The car will need to be retuned of course.

 

LQ9 is a gen III. never made a LQ9 gen IV.

And you can do 450 on a 6.0. So save yourself some $$$. But then again, guys have made 450 with bolts ons and a cam in a 6.2. No need for heads. What heads do you plan on going with?

 

I know I can get 450 on the 6.0, but I know how bad the 6.2 is cause I have one, lol. With the 6.0 I was looking at getting PRC heads from Texas Speed and Performance.

Guess I'll start looking for a gen 3 6.0, alot less work in the swap and I'm sure I can get more than enough power out of it.

 

6.2....

 

Boost the 4.8....

 

^2

just spend the money for the money on a turbo kit you can find cheaper then you will pay for new motor.
if all you want is 450 then turbo the 4.8 you can use kit later on also.
if you want to have room to grow later down the road go with the 6.2 keep the stock heads and just head stud them. later on you can through charger or turbo and easily make 600hp
if you want a good N/a motor that go with the 6.0 it can be good for 400-450 with bolt ons but heads dont flow as good 6.2 if you ever decide to charge it.
lots of power has been made on stock heads cathedral or square port.