Bought core block

Today I jumped the gun and bought a shortblock 5.3 included that seems to be from the 99-06 generation that I was going to rebuild just for a backup to go in a 2008 tahoe. The guy I purchased it from said it ran but burned oil due to high mileage.Im able to turn the engine by hand so thats a plus. I am in the process of removing the rocke arms and heads. I was doing some research and see the horsepower changed between the years and does anyone know if it was the programming or engine internals that changed that made the extra hp?

lspann3525 said:

I was doing some research and see the horsepower changed between the years.
Does anyone know if it was the programming or engine internals that changed that made the extra hp?

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Biggest change was switching from mechanical fan to electrical fans.
Besides that, rectangle heads do have better high-RpM flow compared to pope hat heads
(not sure about low-RpM flow, think VVT makes up for this).

Could this block be possibly 2006 because of the last digit

I was trying to decode this so I can tell which year but not finding much info??

The number below tells me its a 4.8l / 5.3l block 99-06

@lspann3525 Many factors can contribute to the power rating like heads, pistons, and cam. There is a bit of work to get a GMT800 motor into a GMT900 chassis but it should be doable. Was it a good deal or why did you buy it?

Umm. I think you should have bought a Gen IV core to keep everything more simple.

The major difference between the Gen III and IV on the block are:

1.) 24X vs 58X crankshaft reluctor wheel. The wheels themselves can be swapped from one to the other, however. But needs to taken to a machine shop unless you want buy the Goodson tool. Obviously, crankshaft is coming out for this.

2.) Camshaft position sensor and count. Gen III has the cam sensor on the rear/top of the engine and it's a 1X reluctor. Gen IV has the cam sensor on the cam sprocket and is a 4X reluctor. An LS2 cover will get you the provisions for front cam sensor and there's a conversion harness that goes from a Gen IV to Gen III... I'm not sure if there's anything the other way around, but I'm sure you can do it.

3.) Knock sensors are on the top inside the valley cover on Gen III vs down on each bank on Gen IV. Going from Gen IV to Gen III, there's a harness to convert the different location and the smaller threaded holes can be reamed and retapped for the larger thread of the Gen III knock sensors... I'm not sure what going the other route would entail.

4.) I'm sure there's other smaller stuff to consider...

So to summarize, I'm sure it is possible, but you can see there's plenty involved. I'm assuming no DoD/AFM stuff would get reused, of course.

I felt it was a good deal I got everything except for the wiring harness and computer. Came with a engine stand. Over the last couple of nights Ive removed the heads, camshaft, pistons and crank. None of the bearings seem to spun everything looked good for a high mileage engine. Im going to drop the block off at the machine shop and have them check the bearings (cam, freeze plugs and main bearings). I thought about reusing the crank but being high mileage I may need to replace it along with cam,oil pump and timing chain.

I did notice the reluctor will on this crankshaft unlike the crankshaft in the 08 5.3l. Are there any upgraded cranks or improvements or is the factory cranks stable?

lspann3525 said:

I felt it was a good deal I got everything except for the wiring harness and computer. Came with a engine stand. Over the last couple of nights Ive removed the heads, camshaft, pistons and crank. None of the bearings seem to spun everything looked good for a high mileage engine. Im going to drop the block off at the machine shop and have them check the bearings (cam, freeze plugs and main bearings). I thought about reusing the crank but being high mileage I may need to replace it along with cam,oil pump and timing chain.

I did notice the reluctor will on this crankshaft unlike the crankshaft in the 08 5.3l. Are there any upgraded cranks or improvements or is the factory cranks stable?

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You can probably buy a new crank with the right reluctor wheel from Summit. I believe there is also a company that makes a converter box for the signals to convert them to the newer standard. Might be worth a Google search to see it you can find such a beast if needed.

Wait until the machine shop takes it apart. I recently tore down my LQ4 with 262k miles for a refresh and the crank journals looked excellent. Should have taken a photo. I didn't even bother "mic"-ing it.

The LS cranks are very robust and made from nodular iron (also called ductile iron). Folks push 800-1,000 HP through them on highly modified engines with stock bottom ends. If the journals look good, there's absolutely no reason to replace it in my opinion. Get the reluctor wheel swapped by the machine shop. I think my local shop charges $100 for this plus the part.

IIRC, the Summit Racing LS cranks are turned down. Maybe 10 thou or something like that?

@Geotrash I think the Lingenfelter converter box converts 58X to 24X, but not the other way around. But OP should look into that to confirm...

Look at Summit. They have a Pro Series kit to turn the 5.3L into a 6.6L/400cc stroker monster. Kits come with matching cam and rotating assembly. Not sure on pricing but good to know when starting from a freshly machined block.