Don’t let the numbers in the engine codes of the LS series lead you to believe that they correspond with their introduction. While the LS1 is the first Gen 3 LS engine, it wasn’t followed by engines with the following numbers. The LS6 engine, for instance, came right after the LS1 while the LS2, LS3, and LS4 were introduced much later.

While we are on the subject of names, it’s important to mention that this wasn’t the first time General Motors was using the LS6 designation. It was first used in the 1970s for a gigantic 7.4-liter V8 engine. The latest and more relevant application though was as a Gen 3 LS engine. Like the engine that first used the designation, the LS6 was a high-performance offering.

The LS6 may not be as commonly spoken about as some other engines from the LS engine series, but it still makes for a good swap option even today. Here’s everything you need to know about it.

Is an LS6 a 454?

No, the LS6 is not a 454. Before we go any further it’s important to clear any confusion about the LS6 in question. While the original LS6 from the 1970s was a 454 cu in unit, the comparatively newer one is 346 cu in. 

V8 engines were downsized significantly over the years as they needed to be more efficient – and thanks to advancements in tech – they were able to do so while gaining performance.

What’s Better LS1 or LS6?

The LS6 is better if you want better performance. Just like every beastly engine should be introduced, the 346 cu in (or 5.7-liter) LS6 engine debuted in the high-performance version of an already sporty car vehicle. This was a clear indicator that this engine meant business. The engine was first seen in the 2001 Chevrolet Corvette Z06 and featured improvements over the standard LS1.

General Motors didn’t change a lot in terms of basic specifications and the LS6 shared aspects like the block design and its size with the LS1. What differentiated it was the changes they’ve made to boost performance. This included changes like a less restrictive intake, stronger valvetrain, and camshaft designed toward delivering stronger performance. The Corvette also used a different titanium exhaust that helped the engine flow more air while also weighing less. 

The LS6 was first made available with 385 HP and that figure went on to get bumped to 405 HP later. Torque, meanwhile, was also quite impressive at 400 lb-ft. These figures were quite a bit more than what LS1 had to offer, and it also delivered a noticeable performance gain in the real world.

LS6 Engine Specifications

As you’d expect, the additional performance offered by the LS6 was a result of quite a few mechanical changes. However, before we get them, here’s what remained quite similar. Like the LS1, the LS6 is a pushrod V8 that uses a 90-degree cylinder angle. The bore and stroke also remained unchanged. In fact, the majority of the bottom end is the same as the LS1.

The LS6 uses a cast-iron crankshaft and aluminum pistons which feature a hypereutectic coating. The connecting rods, meanwhile, are identical to the ones on the LS1 engine. When it comes to the cylinder head, the LS6 has a unique design while still being made out of aluminum. As for the head, General Motors tweaked it to have a smaller combustion chamber. Thanks to this, the engine had a higher compression ratio of 10.5:1. 

Another small change came in the form of a differently shaped exhaust port. The LS6 makes use of a D-shaped port. The engine also made use of intake and exhaust valves which were made out of steel. The LS6 was used in two cars and featured different camshafts for these applications. While the exhaust system used by the LS6 is quite similar to its predecessor, it uses a higher-flowing intake manifold. This meant the engine was getting a higher supply of air. The company also upgraded the fuel injectors, as more airflow has to be met with more fuel.

While some LS engines did feature a racing-inspired dry-sump system, the LS1 didn’t. It made use of a conventional wet sump. Speaking of the oil system, the LS6 featured improvements to the crankcase ventilation system which was more efficient at gathering crankcase gas.

What Did LS6 Engine Come In?

The General Motors LS6 engine was used in two “regular” production cars, as well as in a heavily modified state in the 2007 SSC Ultimate Aero TT.

• 2001-2004 Chevrolet Corvette C5 Z06
• 2004-2005 Cadillac CTS V-Series
• 2007 SSC Ultimate Aero TT

What Makes the LS6 Engine So Good?

As we mentioned above, the LS6 was a huge improvement over the LS1 engine. However, that wasn’t all that made it so good. When the engine was introduced and people got to first experience it, it was said to be quite the performer. It is also said that it was really enjoyable to shift gear just shy of its rev limiter at 6,500 RPM.

The LS6 brought a lot more top-end performance than many expected. In fact, it had more punch not just at the top-end but throughout the rev-range when compared to the LS1. These are just some of the highlights of the LS6 engine.

Can the LS6 Engine Be Modified?

While the LS6 engine is quite potent right out of the box, the numbers can be bumped up with certain modifications. Interestingly, the LS6 has developed a reputation for offering the perfect balance of power and reliability in stock form. Oftentimes, the engine is used in race applications without any modifications.

Even so, the LS6 engine is a solid platform to work on, and it’s quite easy to extract an additional HP from it using pretty much only bolt-ons. Basic modifications like a cold air intake, headers, and an exhaust system will unlock quite a bit of the engine’s potential. However, to get the most out of these modifications, the engine requires an ECU remap. Reports also suggest that a colder thermostat helps with this purpose as it allows for tuners to dial in more aggressive ignition timing. 

While the LS6 intake was an improvement over other LS engines, it was paired with a throttle body that proved to be a limiting factor. A common upgrade is to swap the throttle body for a 4 bolt unit that opens up the possibility of making more power. The stock throttle body is a 78 mm unit, and it can be swapped with a 90 mm or 102 mm unit. 

The LS6 engine starts suffering from fueling issues once you get to the 420 HP mark. At this point, it’s wise to upgrade the injectors and the pump to allow for a higher flow of fuel. Once this is done, the engine can be supercharged or equipped with a nitrous oxide system. It’s quite easy to reach the 600 HP territory with these modifications. If you are on a quest for more power, the engine will require more serious modifications – like forged pistons, connecting rods, and more.

LS6 Common Problems

While the entire LS engine series has proven to be quite reliable, there are certain issues one has to look out for.

Cracked Valve Springs

The LS6 engine is known to have valve springs that can crack. The LS6 has a total of 16 valve springs to support the 16 valves it uses. When these springs crack, they don’t have enough tension to help with the operation of the valves. 

This causes the valve to not close fully or end up falling into the cylinder. At this stage, the engine loses compression and can end up facing major damage if it comes in contact with the piston. While this problem is most common on the engines made from 2002, it can also occur in other production years.

Oil Consumption

Reports and a service bulletin from General Motors state that the LS6 engine suffers from an oil consumption problem. While it’s not uncommon to see some high-capacity engines consume oil over an extended period, engines made from 1999-to 2002 tend to consume more oil than normal. According to the service bulletin, the problem was caused by “the PCV baffle not being properly sealed to the valley cover, causing oil to enter the PCV system.”

Bad Rocker Arm Bearing

Another problem with the early production years of the LS6 engines concerned the rocker arm bearings. These bearings would go bad and affect the functioning of the rocker arms. And the rocker arms play a big role in making the engine function correctly. When these bearings fail, it can cause major damage which is why it’s important to swap them out for a fresh set on a higher mileage example.

Find LS6 Engine Parts Right Here!

Do you have an LS6 engine or considering getting one? Here at Newpats.com, we’ve got your back! Our extensive catalog includes a wide range of genuine, OEM and quality aftermarket parts for a numerous GM engines and vehicles. 

All you need to do is select your car from the drop-down menu, and you’ll be able to search for products that are a guaranteed fit for your vehicle. If you’re running a swapped LS, select the car that came with that LS from the factory.