Hey I'm new to the site and I have a question and I'm not sure if this is the right spot but I just got a 5.3 short block but once I opened the box and looked it has flat top piston so is there any way to measure if it's a 4.8 in a 5.3 block?

 

The block is the same between a 5.3L and the 4.8L only the crank, rods and pistons change.

If it's aluminum it could be an L33

If it's iron, it's likely a 4.8L

Would need to know the year of the engine or would have to see pictures of what you have to know for sure.

 

 

That is a Newer gen 4 aluminum block. Looks like it could be a 5.3L

To confirm, Turn the crank over until you see an 8 digit part number.

If the last 3 digits are 216 its a 5.3L. Should be 12552216

If the last 3 digits are 482 its a 4.8L. Should be 12553482

 

Well hopefully you wanted a Gen IV...... because that is a Gen IV aluminum block 5.3.... so it would have that lovely AFM trash in it most likely. No VVT at least lol.

 

Thanks a lot man!

 

It was supposed to be a gen lll would you say the gen lV is better?

 

The Gen 4 does have some nicer features.

If you need it to work on a gen 3 system a few thing will need to be done.

The wheel on the back of the crank will need to be changed to a 24X

You will need a front cover for a cam gear sensor and the cam gear will need to be changed to I believe a 1x.

You will need an adapter harness to reach the new locations for the sensors.

The last would be the knock sensor's. They will need to be relocated to the side of the block. You will need to drill and tap for the hold style sensors in order for them to work. You also need an extension harness for that as well.


I will be doing a build up soon, using a Gen 4 5.3 engine into a gen 3 style vehicle.

 

Mine is going into a 1995 1500 lol so it's gonna be a fun build family project

 

1Fastbrick gave you the rundown. You will need to delete the active fuel management while you have it apart. If you are doing a swap and don't have a harness yet you can just use a Gen IV harness setup and go that route. It is an aluminum block 5.3 with flat tops and the full floating pin rods so it's not a bad setup at all.

I am in the middle of putting a crate LS3 in my 1990 K5 Jimmy and I bought a harness from PSI to do the swap with. You can build your own too if you want too. Totally up to you though!