LS1, LSA, LSX: What is the Difference?

When you think about an LS engines, a few bread winners come to mind — such as the LS1, LS3, and LS7. But many people don’t know that there are currently 30 different versions of LS engines. These range from 5.3L truck engines; to race versions of production engines; to the LSX which was never sold in a production vehicle. To the average guy looking to pick up a vehicle to use an LS engine, this can seem a little overwhelming. Especially since the “L98” is not really an LS engine at all.

I figured I’d put together a little blog laying out the LS engine family and my personal take on my favorites. To keep this from becoming a blog of epic proportions, we are just going to look at the car based LS engines since those are the most popular for every-day performance.

Gen III Engines

The Gen III Engines include the LS1 and the LS6. These engines are very similar in that they both share a 5.7L displacement, but with different heads and intake. On the LS6, GM bumped up the strength of the block and installed a higher flowing intake manifold and MAF sensor. It also used the “243” heads, which refers to the casting number. Most of the engines have the sodium filled valves that were also used along side a higher lift camshaft to up the power over the LS1. But that is all from the factory. The aftermarket groups these engines together and because they are so similar, power output is very similar.

There is no advantage or reason to choose a LS1 or LS6 if you don’t have an engine to start with. If you must have an early LS due to budget, and you plan to keep things OE — such as the cam and intake manifold, then go with the LS6. But if you own an LS1, than finding a used LS6 to swap in or pull parts from might not be a bad idea. Just remember, there is no substitute for aftermarket parts.

Gen IV Engines

In 2004, GM redesigned the LS platform to accept their newly designed Active Fuel Management and later introduced the square-port head technology featured in the L92, LS3, etc.

Here is the list of Gen IV LS engines, excluding the truck Vortec line of engines:

  • LS2
  • L76
  • LS3
  • L99
  • LS4
  • LS7
  • LS7.R (Also known as the C5R)
  • LSX
  • LS9
  • LSA

Let’s start by talking about a wierd little engine – the LS4.

Yup, it is sitting the wrong way in the engine bay.

LS4 you ask? Oh yes there is one such engine, and it is the red headed step child of all the LS engines. This engine was developed for use in front wheel drive vehicles. Its block design is shared with the Vortec engine of the same displacement, but is cast from aluminum. The crankshaft had to be shortened 13 mm to fit in it’s required applications and it was the first LS engine to get GM’s Active Fuel Management technology. Not too much aftermarket development has been done with these engine as the platforms they were offered in never really were geared toward performance.

You could find it in:

  • 2006-2009 Chevrolet Impala SS
  • 2006-2007 Chevrolet Monte Carlo SS
  • 2005-2008 Pontiac Grand Prix GXP
  • 2008 Buick LaCrosse Super

The LS2 is the 6.0 L LS engine that was best known in the Corvette, CTS-V, and GTO of just a few years ago. It uses the same 243 heads from the LS6, but you won’t get the fancy valves. But there is no replacement for displacement, which is the reason the LS2 was rated at a higher horsepower. This engine even had a less aggressive camshaft and depending on where it came from power was usually around 390 – 400 hp. The 400 number is what was found in the GTOs and Corvettes, while the 390 hp number is for the ones that came from the trucks due to the different intake manifold. Although the trucks had much more torque at lower RPM as a result.

From there GM took the LS2 and added their Active Fuel Management – the L76 was born. But because all of that technology is in the heads, they had to be completely redesigned. GM worked with their Holden division on this engine and decided to make their changes with the biggest being the port design. The LS2 uses a cathedral port, while the L76 has a square port. The square port allows for more airflow which means more power. This engine is only offered in America in the G8 GT, so you wont see to many of these except in the G8s, but the head design is very popular in the aftermarket.

Because the Holden cars do not use the Active Fuel Management, they decided to take the L76 and strip all the components designed into the engine off – which spawned the L98. This engine is the same as the L76, but the heads do not feature all the components necessary for Active Fuel Management. This engine was never sold in the US but it does however have the square port design that have become a popular design for aftermarket companies to use when casting their own heads. Even GM decided to use them on the Corvette’s new base model engine, the LS3.

The LS3 – the Engine for the Rest of Us

The LS3 block is very similar to the LS2. It does however have a slightly larger displacement increased to 6.2 L. While the head design is the same as the L92, it is what is inside them that counts. GM fills these with hollow stem valves that are a larger diameter than the LS2 for more performance. The LS3 intake manifold is also better flowing and gives the engine more air and mo’ power. This is also engine found in the 2010 Camaro SS.

LS7: All Air Monster

The LS7 is the largest engine offered in the LS street production line up currently at 427 cubic inches. This engine shares little with the other Gen IV engine other the basic design. Everything about the bottom end of the engine is light: light weight rods, pistons, and even the crank is lightened, all for better NA performance. Up top the heads are all unique to this engine, with hollow stem valves and ports that do not share much with the LS3/L92. The list goes on from there as this engine has a strong history in racing and a lot of technology. From the factory this is the best engine from GM for unmodified/un-supercharged performance. I mean the engines are even all hand build. That is something you don’t hear everyday.

Now, that being said. The LS7 is an expensive engine. For my projects, I will go with the LS3 – big power for an everyday price. We have had a few LS3’s come through our shop, and with only a few upgrades such as intake, exhaust, and a cam, they make as much, or more power than the stock LS7.

Now let’s take a look at the supercharged engines in the LS family: LS9 and LSA.

Both LS9 and LSA are 6.2L engines biased on the LS3. Before you think that these motors just have a supercharger slapped on – you’d be dead wrong.

Both are built to be 20% stronger than the LS3 short-block, according to GM, and even have forged (LS9) or hypereutectic pistons (LSA) with oil-spray cooling to handle the pushing power. The heads on these engines are similar to the L98/L76/LS3 heads except that they were slightly redesigned to aid in mix the air/fuel being pumped in by the supercharger.

The difference can also be found in the supercharger. The LS9 has a 4-lobe Eaton 2.3 L supercharger on top, while the LSA has a smaller 1.9 L. Both are the most powerful engines offered in their respective cars, the LS9 in the Corvette ZR1, and the LSA in the CTS-V and hopefully the Camaro Z28 one day.

All-Race Engines

The LS7.R and the LSX are two all-out race engines in the family. Both blocks are both based on the production LS7 engine, but their biggest difference are the material used for casting the block. The LS7.R is aluminum while the LSX is a cast iron. Both are designed for serious horsepower and have proved to be real winners – the LSX block having showed it can support over 2,000 hp in forced induction applications. The LS7.R was developed for Grand Am racing and is not for sale. The C5R block uses many of its design features and is for sale through GM Performance Parts.

In terms of aftermarket use, the LSX has everything that the engine builder would want in an affordable design. However, the LS7.R was developed by Corvette racing for use out on the road course and isn’t even for sale. And just because the LSX was made for racing, doesn’t mean that it wouldn’t work well in a street car. The biggest thing when you look at the C5R vs the LSX is the block design. The C5R is cast using the Gen III design while the LSX uses the updated Gen IV design that provides a stronger block due to the way the water passages are designed. However, if you have an ultra-light NA race car or street car, the C5R probably has it’s place.

I hope this has helped educate you a little bit on the differences between these seemingly similar engine. All of these engines are capable of making huge power no matter what car they are installed in. It just all comes down to what you are doing.

Check out the excellent reference article on Wikipedia about the LS engines.

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