LS Engines 101: An Introductory Overview Of The Gen III/IV LS ...

(Updated 02/12/2020)

[Editor’s Note: Find a comprehensive list of every LS and Vortec engine spec guide and upgrade guide we’ve published here.]

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Chevrolet introduced the automotive world to the LS engine with the launch of the LS1 in the 1997 Corvette C5.

It left a mark.

The lightweight engine made big-block horsepower in a package no bigger than the engine-swapping community’s previous hero—the small block Chevy. Not only did the LS engine platform provide opportunity for making unprecedented power in a small-block mill, it did so while meeting modern fuel economy and emission standards.

In an automotive context, it’s not hyperbole to say the LS engine changed the world.

Because LS blocks share similar exterior dimensions, the vast majority of LS engines can fit anywhere that a small block Chevy 350 can. They’re ideal for both tame daily driver builds, as well as high-performance street or race applications north of 1,000 horsepower.

We know you get it—LS engines are really popular. Even better—they’re pretty easy to find. Both factory and aftermarket LS parts are readily available. And dropping an LS motor into another vehicle—particularly any car or truck previously powered by a small block Chevy—is as simple as engine swapping gets.

As is often the case, the devil tends to be in the details. So we’re going to deliver those details, and we’re not going to take anything for granted in the process.

There are several engines within the LS family. So if you’re going to swap or modify an LS, the first thing you’ll need to know is which particular engine you have or want, and how to find it (should you choose to not go with one of the many LS crate engines available). That means understanding the various technical nuances of each LS RPO code, so you know which new parts to buy, or what old parts to salvage on your next trip to the junkyard.

Know Your LS Engines

Even among experienced mechanics and auto enthusiasts, there is a lot of confusion about General Motors’ naming convention for the LS engine series. We’re going to clear up as much uncertainty as we can.

1. It Doesn’t Have to Say “LS” to be an LS Engine (Hello, Vortec)

It was automotive enthusiasts who gave the “LS Engine Series” its name.

Officially, there’s no such thing. What we call the LS engine series is really just all of the engines from General Motors’ Gen III and Gen IV small-block V8 groups.

If you want, you can imagine the LS engine series kind of like a group of celebrities—people like Oprah Winfrey and Ben Affleck—who were given honorary doctorates from Ivy League universities, and then afterward everyone actually started calling them Dr. Winfrey and Dr. Affleck.

“Congratulations, Dr. Affleck. I thought you were amazing in Gigli, and your interpretation of Batman is definitely just as good as Christian Bale’s,” the president of Brown University probably said.

Much like that very realistic scenario, Chevy’s L76 and L77 engines are actually LS engines.

And though the majority of people might call them Vortec engines, GM’s small-block 4.8L, 5.3L, 6.0L, and 6.2L truck engines from 1997 through Gen IV are still very much members of the LS engine family.

The LS1 was the first mill from GM’s Gen III small-block engine platform. Then, the 385-hp LS6 made its appearance in the 2001 Corvette Z06, and everyone just sort of latched onto the “LS series” name.

But if we’re going by the book (and we’re not—we just want you to get it), the LS1 and LS6 are just two of several Regular Production Option (RPO) codes in GM’s Gen III engine book.

In fact, there have already been LS engines—the original Chevy 454, for example. It was introduced in 1970 and came in three variants: the LS5 (an RPO code you won’t find in the modern LS family), the LS6, and the LS7. So, if you’re one of the people who think it’s all a little confusing, you’re not weird. It’s actually confusing and you probably don’t need a lobotomy.

There are at least 25 RPO codes within the LS engine platform that don’t contain the letters “LS” at all (though they do all begin with the letter L). You’ll find the full list below in our LS Engine Family Tree.

2. The LS Engines Were Not Released in Sequential Numerical Order

This should be obvious if you paid attention to that last note. But it might bear repeating. Even though it would make sense to the majority of people, GM didn’t release the LS2 immediately after the LS1. That would have made it too easy. The LS6 came next.

But GM also launched two LS truck engines before unleashing the LS6—the 4.8L Vortec (LR4) and the 5.3L Vortec (LM7, L59, LM4, L33). Sometimes, the only differentiator between these engines is the block material: cast iron or aluminum—another subject we’ll dive into further as we explore the LS engine universe.

3. ‘Wait a Minute… We Can Use Easy-to-Find Truck LS Engines for Swaps?’

Yep. Fun, right?

But there are all sorts of Ifs, Ands, and Buts to think about, depending on your specific application. We’ll tell you as much as we can. Near the bottom of this article, you’ll find a still-growing list of LS and LS-based truck engine specification guides and comprehensive engine upgrade guides. These guides are full of all kinds of expert LS-engine wisdom, courtesy of our friends at Summit Racing.

4. One of These Things is Not Like the Others (Spoiler: It’s the LS4)

The LS4 is the oddball of the LS series. There’s a VERY good chance that it’s not your friend and will openly mock that Def Leppard poster you have hanging in your garage.

The LS4 is designed specifically for transverse front-wheel drive applications, unlike every other LS-based RPO code. Unless you like to fabricate (a lot!), you’ll probably save yourself trouble by steering clear of the LS4.

5. Don’t Confuse Gen III—the First Half of LS Engine History—with “LS1”

You’ll sound silly AND get the wrong parts—two things best avoided. We have it on good authority that several people refer to ANY LS engine from the third generation of Chevy small blocks as an “LS1.” It would be helpful to everyone in the world if that stopped happening.

There are several ways to identify an LS engine, and we intend to teach you all of them.

One way is simply to know which LS engines came in which GM vehicle models (if you can be sure a particular vehicle is housing its original engine).

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READ:

• LS Engine Spotter’s Guide, Part 1: Matching the Vehicle to the Engine

• LS Engine Spotter’s Guide, Part 2: Matching the Engine to the Vehicle

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The lifetime of the LS engine series can be split in two halves—Gen III and Gen IV. Gen III spanned from 1996 to 2007. And Gen IV spans from 2005 through today. With the all-new Gen V 6.2L LT1 (released for the C7 2014 Corvette Stingray), new LS engine production could be nearing its end, but we assure you that people using LS powerplants to make their vehicles go won’t stop for a very long time.

To wrap your head around the group of engines that make up the LS engine family, we think it’s helpful to understand the architecture of the LS family tree, so we’re going show you how that looks.

The LS Engine Family Tree

Forgive us for not making it actually look very family tree-like. But this is a high-level look at the LS engine family that you might find useful.

LS Car Engines - Generation III (1996-2007)

Displacement	RPO Code
5.7L	LS1
	LS6

LS Vortec Truck Engines - Generation III (1999-2007)

Displacement	RPO Code
4.8L Vortec	LR4
5.3L Vortec	LM7
	L59
	LM4
	L33
6.0L Vortec	LQ4
	LQ9

LS Car Engines - Generation IV (2005-Present)

Displacement	RPO Code	Notes
5.3L	LS4	*Only LS engine with unique transverse FWD motor mount design
6.0L	LS2	*GM put the LS2 engine in both cars and trucks
	L76	*GM put the L76 engine in both cars and trucks
	L77
	L98
6.2L	LS3
	L99
	LSA	*Supercharged
	LS9	*Supercharged
7.0L	LS7

LS Vortec Truck Engines - Generation IV (2007-Present)

Displacement	RPO Code	Notes
4.8L Vortec	LY2
	L20
5.3L Vortec	LH6
	LH8
	LH9
	LY5
	LMF
	LMG
	LC9
6.0L Vortec	LS2	*GM put the LS2 engine in both cars and trucks
	L76	*GM put the L76 engine in both cars and trucks
	LY6
	L96
	LC8
	LFA
	LZ1
6.2L Vortec	L92
	L94
	L9H

Bonus LS Engine Notes:

• LS engine blocks are either cast iron or aluminum. All car engines had aluminum blocks. Truck engines could be either material.
• With the noted exception of the early LQ4 engine, all LS engines have aluminum cylinder heads.
• The LS2 and L76 are noteworthy in that they are both Gen IV 6.0L aluminum block engines, and that they came from the factory in both cars and trucks. Each came with different accessory drives, intake manifolds, and oil pans. They also had different VIN codes.
• The LS364 is a carbureted Gen IV crate engine GM makes exclusively for the aftermarket.
• LSX came to market as a bare engine block for retrofitting and swapping, and is now available as both an LSX 454-cubic-inch (7.4L) crate engine, and LSX 376-cubic-inch (6.2L) crate engine.

LS Engine Spec Information & Engine-Specific Upgrade Guides

We created a series of comprehensive LS engine spec guides and engine upgrade guides by RPO code. You can find them all here:

Gen. III LS Engine Upgrade Guides & Specs (1996-2007)

Gen III LS & Vortech Engines
Displacement	Engine Code	LS Engine Upgrade Guide	LS Engine Spec Guide	Reluctor	VIN (8th Digit)	Block	Head	Gen III Years	Vehicle
4.8L	LR4	LR4 Upgrade Guide	LR4 Engine Specs	24X	V	Iron	Cathedral	1999-06	Truck/SUV/Van
5.3L	LM4	LM4 Upgrade Guide	LM4 Engine Specs	24X	P	Alum.	Cathedral	2003-05	SUV
5.3L	LM7	LM7 Upgrade Guide	LM7 Engine Specs	24X	T	Iron	Cathedral	1999-07	Truck/SUV
5.3L	L59	L59 Upgrade Guide	L59 Engine Specs	24X	Z	Iron	Cathedral	2002-07	Truck/SUV
5.3L	L33	L33 Upgrade Guide	L33 Engine Specs	24X	B	Alum.	Cathedral	2005-07	Truck
5.7L	LS1	LS1 Upgrade Guide	LS1 Engine Specs	24X	G	Alum.	Cathedral	1997-04	F body/C5/GTO
5.7L	LS6	LS6 Upgrade Guide	LS6 Engine Specs	24X	S	Alum.	Cathedral	2001-05	C5 Z06/CTS-V
6.0L	LQ4	LQ4 Upgrade Guide	LQ4 Engine Specs	24X	U	Iron	Cathedral	1999-07	Truck
6.0L	LQ9	LQ9 Upgrade Guide	LQ9 Engine Specs	24X	N	Iron	Cathedral	2002-07	Truck

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Gen. IV LS Engine Upgrade Guides & Specs (2005-Present)

Gen IV LS & Vortech Engines
Displacement	Engine Code	LS Engine Upgrade Guide	LS Engine Spec Guide	Reluctor	VIN (8th Digit)	Block	Head	Gen IV Years	Vehicle
4.8L	L20	L20 Upgrade Guide	L20 Engine Specs	58X	A	Iron	Cathedral	2010-17	Truck/Van
4.8L	LY2	LY2 Upgrade Guide	LY2 Engine Specs	58X	C	Iron	Cathedral	2007-09	Truck
5.3L	LY5	LY5 Upgrade Guide	LY5 Engine Specs	58X	J	Iron	Cathedral	2007-09	Truck/SUV
5.3L	LC9	LC9 Upgrade Guide	LC9 Engine Specs	58X	3 or 7	Alum.	Cathedral	2007-14	Truck/SUV
5.3L	LH6	LH6 Upgrade Guide	LH6 Engine Specs	24X/58X	M	Alum.	Cathedral	2005-09	SUV
5.3L	LH8	LH8 Upgrade Guide	LH8 Engine Specs	58X	L	Alum.	Cathedral	2008-09	Truck/SUV
5.3L	LH9	LH9 Upgrade Guide	LH9 Engine Specs	58X	P	Alum.	Cathedral	2010-12	Truck
5.3L	LMF	LMF Upgrade Guide	LMF Engine Specs	58X	4	Iron	Cathedral	2010-14	Vans
5.3L	LMG	LMG Upgrade Guide	LMG Engine Specs	58X	0	Iron	Cathedral	2007-14	Truck/SUV
5.3L	LS4	LS4 Upgrade Guide	LS4 Engine Specs	24X/58X	C	Alum.	Cathedral	2005-09	FWD car
6.0L	LS2 (Car)	LS2 (Car) Upgrade Guide	LS2 (Car) Engine Specs	24X/58X	U	Alum.	Cathedral	2005-2007	Corvette/GTO/CTS-V
6.0L	LS2 (Truck)	LS2 (Truck) Upgrade Guide	LS2 (Truck) Engine Specs	24X/58X	H	Alum.	Cathedral	2005-06, 2007-09	SSR/TBSS, TBSS/9-7X Aero
6.0L	L76 (Car)	L76 (Car) Upgrade Guide	L76 (Car) Engine Specs	58X	Y	Alum.	Rectangle	2008-10	Pontiac G8
6.0L	L76 (Truck)	L76 (Truck) Upgrade Guide	L76 (Truck) Engine Specs	58X	Y	Alum.	Rectangle	2007-09	Truck/SUV
6.0L	L77	L77 Upgrade Guide	L77 Engine Specs	58X	2	Alum.	Rectangle	2011-17	Caprice PPV, Holden VE2/VF
6.0L	L96	L96 Upgrade Guide	L96 Engine Specs	58X	G	Iron	Rectangle	2010-17	Truck/SUV/Van
6.0L	L98	L98 Upgrade Guide	L98 Engine Specs	58X	N/A	Alum.	Rectangle	2007-08	Holden
6.0L	LC8	LC8 Upgrade Guide	LC8 Engine Specs	58X	B	Iron	Rectangle	2011-16	CNG fuel
6.0L	LFA	LFA Upgrade Guide	LFA Engine Specs	58X	5	Alum.	Cathedral	2008-09	Hybrid Truck/SUV
6.0L	LY6	LY6 Upgrade Guide	LY6 Engine Specs	58X	K/N	Iron	Rectangle	2007-14	Truck/SUV/Van
6.0L	LZ1	LZ1 Upgrade Guide	LZ1 Engine Specs	58X	J	Alum.	Cathedral	2010-13	Hybrid/Truck/SUV
6.2L	L92	L92 Upgrade Guide	L92 Engine Specs	58X	8	Alum.	Rectangle	2007-08	SUV
6.2L	L94	L94 Upgrade Guide	L94 Engine Specs	58X	F	Alum.	Rectangle	2010-14	SUV
6.2L	L99	L99 Upgrade Guide	L99 Engine Specs	58X	J	Alum.	Rectangle	2010-15	Camaro (auto)
6.2L	L9H	L9H Upgrade Guide	L9H Engine Specs	58X	2	Alum.	Rectangle	2009-14	Truck/SUV
6.2L	LS3	LS3 Upgrade Guide	LS3 Engine Specs	58X	W	Alum.	Rectangle	2008-17	Performance Cars, C6 Grand Sport
6.2L	LSA	LSA Upgrade Guide	LSA Engine Specs	58X	P	Alum.	Rectangle	2008-15	CTS-V, 5th Gen ZL-1
6.2L	LS9	LS9 Upgrade Guide	LS9 Engine Specs	58X	T	Alum.	Rectangle	2009-13	Corvette ZR-1
7.0L	LS7	LS7 Upgrade Guide	LS7 Engine Specs	58X	E	Alum.	Square	2006-15	C6 Z06, Camaro Z28

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(OnAllCylinders contributors Paul Spurlock and Brian Nutter from Summit Racing contributed to this article.)