Before you begin your engine project, you need to know exactly what you have—and when it comes to General Motors’ 3rd and 4th generation LS small blocks, that may not be an easy question to answer.

The LS engine is becoming the go-to choice for many engine swaps. But there are plenty of variations within the LS engine family, so it’s important to know which specific LS motor you’ve got. (Image/Summit Racing)

How Do I Know Which LS Engine I Have?

There are more than 40 variations, including the LS-based Vortec truck engines.

The similarities between them make several LS parts interchangeable, but there are critical differences too. To ensure you’re using the the right parts, you need to know which LS engine you’re starting with.

There are two easy ways:

1. The 8th digit of the VIN

2. By visual inspection

The easiest way to tell the difference is to check the 8th digit of the Vehicle Identification Number (VIN) on the original vehicle. (See below.)

If you don’t have the VIN, you can still identify the engine by visual inspection if you know what to look for. The LS experts at Summit Racing created an interactive tool to help you easily make a positive ID by answering a few questions.

Check out the interactive tool here

Just answer a few basic questions and the tool will be able to tell you what LS engine you have (or at least really narrow down your options).

Please note that this guide is intended for stock engines. If the engine you are looking at has been modified, the guide may not give you the right answer.

How to ID an LS Engine by VIN

Chevrolet’s LS and LS-based Gen III and Gen IV small-block engines are generally known by their RPO code. You can determine the RPO code if you have the VIN from the original vehicle.

  1. Locate the 8th digit of the VIN.
  2. Consult the tables below to identify your engine.

[NOTE: Take care not to confuse the letter “B” and the number “8,” or the letter “O” with the number “0.”]

Gen. 3 LS Car Engines

8th Digit of VINRPO CodeDisplacementCommon Name

Gen. 3 LS Truck Engines (Vortec)

8th Digit of VINRPO CodeDisplacementCommon Name
Iron Block
VLR44.8LVortec 4800
TLM75.3LVortec 5300
ZL595.3LVortec 5300
ULQ46.0LVortec 600
NLQ96.0LVortec H.O. 6000, VortecMax
Aluminum Block
PLM45.3LVortec 5300
BL335.3LVortec H.O. 5300

Gen. 4 LS Car Engines

8th Digit of VINRPO CodeDisplacementCommon Name (Notes)
CLS45.3LLS4 (FWD Only)
PLSA6.2LLSA (Supercharged)
TLS96.2LLS9 (Supercharged)

Gen. 4 LS Truck Engines (Vortec)

8th Digit of VINRPO CodeDisplacementCommon Name
Iron Block
CLY24.8LVortec 4800
AL204.8LVortec 4800
JLY55.3LVortec 5300
0 (zero)LMG5.3LVortec 5300
4LMF5.3LVortec 5300
KLY66.0LVortec 6000
GL966.0LVortec 6000
Aluminum Block
MLH65.3LVortec 5300
3LC95.3LVortec 5300
LLH85.3LVortec 5300
PLH95.3LVortec 5300
5LFA6.0LVortec 6000 (Hybrid)
JLZ16.0LVortec 6000 (Hybrid)
8L926.2LVortec 6200
2L9H6.2LVortec 6200
FL946.2LVortec 6200

NOTE: You can find engine specs and detailed engine upgrade advice for every LS and LS-based Vortec truck engine in one place: The Definitive Guide to LS Engine Specs and LS Engine Upgrades.

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Author: Paul Spurlock