99 lm7 5.3 to 02-06 lq9 6.0 swap
 

Everyone says you are the guys to talk to. And I’m sure for some of you this topic is like :deadhorse:. Looking for some help with my 5.3 to 6.0 swap any info or advice would be appreciated. I am in the planning stages. I would like to do a very clean factory looking swap. I plan on buying a 02-06 lq9 crate motor to swap my lm7 in my 99 Z71 Silverado. As you guys may already know the 99 lm7 only had 270 hp and 315 lb of torque. The 02-03 lm7 made 285 hp 325lb. and the04-07 lm7 made 295 hp 335 lbs of torque. So ya my 99 lm7 is a dog. I have read that a lot of guys have swapped out there lm7 with the lq4 and the lq9 mostly from 02-06 trucks and the stock lq9 is 345 hp and 380 lbs of torque. Maybe with an airaid kit, exhaust and a computer tune, could get close to 400 hp that would sweet in my ½ ton 4x4. So they say everything swaps right over (plug and play) to the 6.0 with no problem. Some say reflash some say not. Some say you need to change the flex plate some say you don’t. Since we know the 99 lm7 is little different because of hp rating. Is any of that a problem with switching over my intake and accessories, exhaust manifolds and flex plate from my 99 lm7 to a 02-06 lq9 crate motor? If not then what do I do about the EGR valve I think was only on the 99s if I reflash the computer to a 6.0? Has anyone done this same swap and can you tell me what I will run into. It’s going to happen one way or another. I can’t wait to get started, just want to know what to expect any help would be great…. THANKS

You will most likely need newer injectors as well as an adjustment to your tune.

The 99's 4.8/5.3 used a 21LBS Injector while the 6.0 used a 24Lbs injector.

From 2000 up, they all used a 24Lbs injector except Flex Fuel models.

The basic long block is similar and will swap out no problem. re use the parts from your LM7

If your buying a pull out motor:

Stay away from the 99-00 6.0l for your swap as they have a longer crank that can only be used with the 4L80E or you need a special convertor.

A 2001-Up LQ4 will have a removable crank spacer and a flat flywheel. You can remove these Items and use the ones from your 99 no problem.

The LQ9 was already mated to a 4L60E so you should not need to change anything.

Just use the intake and exhaust manifolds from your 99 and change the injectors as needed. All the accessories will swap over to the 6.0L

Thanks for the reply. That is exactly the type of info I’m looking for. I had read that the injectors were different on the 99. Thanks for confirming my suspicions about using them. And on the flywheel/ flex plate. You are the man. I have a couple of more questions. Who is the best source for the crate motor? Price and quality. I was just told that the lq9 won’t run well on reg gas it needs super any thoughts on that. And anything else you can tell me would be great. THANKS

I got my Lq9 through a local salvage yard from a wrecked 2005 Escalade. Its obviously better if you can buy straight from the owner so you can get some history of the engine but I was having trouble finding any that route.

The tune will determine what octane fuel you need to run. It can be tuned to run on 87 and up but obviously the higher the octane the more power can be had from the engine. I personally went with a 93 octane tune on mine. Going from my stock 5.3 tune to the lq9 93 octane tune gained me roughly 0.5 seconds in the 1/8th mile.

I run mine on 87. It's a bone Stock Factory LQ9 truck. Only thing it has is a cat back exhaust because the original was all hacked up when I got it.


If your talking a new crate motor, we have many fine sponsors on this board.
If you want a used pull out, Shop around your area and see what you can find. Since you didn't post your location, I am not sure how hard it will be to come by one.

Unless your in CA, because I have one... :devil:

GM LQ4 6.0L 2001-2007 460HP: High Performance Engines | ATK Custom Built Crate Engines

You will be able to swap everything over from your motor. You will need to get a tune when you do the swap. Especially when you switch injectors. You don't want to start a motor with different injectors without a tune. The 8.1 truck injectors are a direct replacement and the are 30 or 31 lb injectors. Very easy for anyone to tune these as all the data is easily found.

I used the 8.1L injectors in my swap, a little over $100 brand new from rock auto.