LS Engines

How to Identify an LS Engine

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)

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.

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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  6. Will 2008 LC9 Drop in 2007 GMC pickup with LH6 engine

    • OnAllCylinders Staff says:

      Externally, most LS engine blocks (regardless of displacement) are darn-near identical save for engine accessory configurations and different intake manifold designs. So physically yes, it should fit in the engine bay without significant issue. The LC9 should also mate to your transmission, as all LS engines share identical output shafts and crank flanges.

      You’re also in luck that your truck was a 2007 model, as that means you had the later version of the LH6 engine that shares a 58X reluctor wheel and the E38-style computer with the LC9.

      Summit Racing’s LH6 Spec Guide and LC9 Spec Guide are good resources to bookmark.

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  9. George Garner says:

    I have a 5.3 envoy engine with the number on back left upper marks 12566910. what engine is this. will it fit in my GMC envoy 2005 serial # 1GKET16M856195030 XL. PLEASE LET ME KNOW

    • Decoding the VIN (I work in parts at a gm dealer) your engine is a LH6 5.3L. It is an early version of the AFM system.

  10. George Garner says:


  11. Serial nr plate on side of block reads PM005028 . Am having trouble with starter not meshing with flexplate. Has holley 4brl n hedman headers. What is it really?????

  12. Devron Forcell says:

    I have a 2000 4×4 ls 5.3 my Mil is do I start my motor back running

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  16. John langsyon says:

    I have purchase a 2001 6.0.LQ4 Question correct me if I’m wrong.. Date cord state B011. 2/1/01 IS THIS RIGHT. Next it has a 3 bolt cam. Numbers on back of block. 12551364.or 12331364?. # SO WHAT GEN ,IS THIS THANKS.

  17. John E Hilldrup says:

    How to identify block out of car or truck where to look for number and how cross type

  18. Wolfram Wysgoll says:

    Hello. So I recently purchased a 2010 Silverado regcab no bells and whistles….yet. its cherry dude like 30k meticulously maintained. I’ve always heard great things in regards to its design I however was unaware this small block was a sleeping monster. I’ve heard you can remove certain inhibitors to unlock power. I was also hoping you could help me out with tuning advice. Thanks Wolf

    • A 2010 most likely has AFM (CYLINDER DEACTIVATION). If not your good, if so there are get arounds. If you have a 5.3 a few easy upgrades would be:
      * port and polish the heads.
      * take the pistons for a 4.8L (flat tops) and the
      connecting rods for a 6.0L and pair them to give you
      engine flat top pistons.
      * add a hot cam (nothing radical. This is also when you
      would want to change out the AFM lifters if needed.
      * finally do a basic programmer tune.

      This would give a good power up and with the right tune even add MPG.

  19. To the writer of this article. At the end you note not to confuse a B for a 8 or a O for a zero. You do know that to prevent this at least for the letter O there is no letter O. There is no O, L, or Q.

  20. Mickey Twomey says:

    I have a 2012 Silverado 5.3 (Vortec5300). 8th digit in my VIN is “7”. Not seeing that in the table for GEN IV LS truck engines?

    Any help?

  21. Hello, I have a gen 4 4.8 or 5.3 motor. I don’t know the vin and am using this motor as a swap into a 1969 chevy truck. Engine block is stamped 12567177. That’s all I can find other than the “IV” and the 4.8/5.3. Where do I go from here to identify the motor. I also need a ecm/pcm and wiring harness. Any help is appreciated.

  22. I have a 2011 Sierra and 8th digit is a 0. Looks like an LMG 5.3. Is that a good engine to install a blower or turbo on?

  23. I have a c199 block with 12560392 nmp3 98 99 00 stamp I can’t find anythinelse out other than the heads are 862 I’d like to know exactly what I have ! The engine is in a 79 cj7

  24. Harry Fitser says:

    I have a 2003 LS motor in a 1953 Oldsmobile Conv The motor came out of a 2003 pick up. The motor Ran great,40 lbs oil pressure hot at idle, Installed in the olds. starts great, 40 lbs oil pressure adoes not over heat but the thermostat does not open (NEW) Radiator gets hot at the top, but cool at the bottom, has stock mechanical fan, air suckes through the radiator and coolant does not bubble out of the radiator any help appreciated

    • Had a Jeep that did a similar thing. It sounds like you have no circulation at all. Have you checked your thermostat to see if it opens? Pull it, test it, and if it doesnt replace it. If that doesnt work then you have air in the system you need to get out that is creating a vacuum. Sounds like your radiator has a cap on it and a drain on the bottom. Remove the cap and get the motor up to temp where the thermostat opens. You can use the upper and lower radiator hoses as kind of pumps by squeezing them (with gloves if they are hot) to push the fluid around forcing the air pocket to the radiator and out the top. Once released your coolant should flow freely and cooling should be consistent.

  25. James Wright says:

    Extremely Excellent!!!!!!


  27. Jesse Hall says:

    I have a 2007 Gmc envoy Denali 8th digit is M what engine can be used to replace my engine

  28. Jesse Hall says:

    Not a mechanic don’t know much abt engines at all .Been at this for 6mos.thank you

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  30. Bennie Greenman says:

    Can a dealership ID my motor if I give them all the ID markes on the block.
    I know absolutely nothing about my short block motor other then I was told it was a LS block I bought only the block no heads.

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  34. Eddie Mecicar says:

    My ECU vin reads “ 86yctj923009rryb” 8th digit is 2 and it’s a 5.3L, non of the tables above are helpful . what is my RPO code?? (2003 GMC Yukon)

  35. Mike Baskin says:

    I have a 5.3 ls gen 3 did a quick flip with good essentials, and had a head gasket leak x2 both sides both motors. I don’t know the donor vehicle and when I try to find head gaskets, they block rear coolant passages. That why leaked . How can I find motor numbers I found a 02f07 not it. Either heads 706 or block is not working can I drill head gaskets so it circulates. I’m lost never had this before but it’s putting oil on top pistons and coolant leaks can’t seat rings like that so I pulled it 3 x please help can’t keep doing this thanks

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