Chevy LS Firing Order Explained

The engine’s firing order refers to the sequence wherein the power event happens in different cylinders. Since there are different types of engines, there are different types of firing orders too. So, what is the firing order for Chevy LS engines?

The firing order for Chevy LS engines is 1-8-7-2-6-5-4-3. This is for a standard cross-plane crankshaft in which the throws are spaced 90° apart and a standard firing order camshaft. It is an upgrade on the firing order of Chevy vehicles’ traditional Small/Big Block engines.

Read on to learn more about the different Chevy LS engines, their firing order, and the so-called “4/7 swap.”

Chevy LS Firing Order Explained

chevy ls firing order

The Chevy LS firing order is 1-8-7-2-6-5-4-3. This is for a standard firing order camshaft and a standard cross-plane crankshaft in which the throws are spaced 90 degrees apart. It is an upgrade on the firing order of Chevy vehicles’ traditional Small/Big Block engines.

The firing order 1-8-7-2-6-5-4-3 does a decent job of firing alternately between banks as much as possible. However, a popular modification is popular as the “4/7 swap.” With this modification, the firing order of cylinders 4 and 7 are switched. We will discuss more of this later.

Chevy LS Engines

Refers to the 3rd and 4th Generation Small Block V8 Gasoline Engines

“LS engine” is the informal name given to the 3rd and 4th generation small block V8 gasoline engines installed in General Motors vehicles. This engine, in which “LS” stands for Luxury Sport, is majorly used in high-end vehicles that offer superb performance, such as the Chevy.

Small Block Chevrolets

The term evolved from the need to distinguish the Gen 3 and Gen 4 small blocks from the original Gen 1 and Gen 2 small blocks. The latter is commonly known as Small Block Chevrolets.

Derived from the Engine Regular Production Option (RPO) Code

The term “LS” is derived from the engine Regular Production Option (RPO) code of the first Gen 3 small block. It was called the LS1 and was initially released in the 1997 Corvette.

“LS engine” identifies all Gen 3 and Gen 4 Small Block Chevrolet vehicles. These include even those that do not form part of LS in their RPO code.

Sometimes Referred to as LSx Engines

These LS engines are sometimes referred to as LSx engines. The small “x” refers to one of the RPO code variations of the engine. However, this term had confused, mainly when General Motors started selling an aftermarket LS cylinder block known as LSX.

The original RPO code LS1 is still being used, but not as often. It consists of the whole Gen 3 and Gen 4 engine family.

Generation 3 Chevy Engines

Released Between 1997 and 2007

The third generation of Chevy engines was released between 1997 and 2007. They are small block V8 engines with a clean sheet design, replacing the first and second-generation engine families, particularly those manufactured in 2002 and 1995.

Consists of an Impressively Strong Engine Block

This LS series consists of an impressively strong engine block. The aluminum engines are almost as durable and strong as the iron generation 1 and 2 engines.

Made Use of the Coil-near-plug Style Ignition

Also, the LS engine made use of the coil-near-plug style ignition. This then replaced the distributor setup of all small block-based engines in the past.

Cylinder Head Pattern

There was the traditional five-volt pentagonal cylinder head pattern in the past. This has been replaced with a square design featuring four bolts only. Also, the pistons consist of flat-topped variations in the following engines:

  • LS1
  • LS2
  • LS3
  • LS6
  • LS7
  • LQ9
  • L33.

The other engine variants, such as the LQ4 and LS9 truck engines, have a dished version of the General Motors hypereutectic piston.

Firing Order

It was during this time that the cylinder firing order became 1-8-7-2-6-5-4-3. This way, the LS series matches the firing order of other modern V8 engines.

Chevy LS1 Firing Order

Initially Launched in the 1997 Chevrolet Corvette

The LS1 engine was initially launched in the 1997 Chevrolet Corvette. It was rated at 345 horsepower (hp) and 350 lb-ft of torque at 4,600 revolutions per minute (rpm) and 4,400 rpm.

Improved Ratings

In 2001, enhancements were made to its intake and exhaust manifolds. This leveled up ratings to 350 hp and 365 lb-ft of torque.

Chevrolet Vehicles Equipped with LS1 Engines

The Chevrolet vehicles equipped with LS1 engines include the following:

  • 1997 – 2004 Chevrolet Corvette C5
  • 1998 – 2002 Chevrolet Camaro Z28
  • 1998 – 2002 Chevrolet Camaro SS

All these Chevy vehicles have an LS1 firing order of 1-8-7-2-6-5-4-3.

Chevy LS6 Firing Order

what is chevy firing order

Higher-output Version of the LS1 Engine

The Chevy LS6 engine is a higher-output version of the LS1 engine, which also retains a similar capacity. Initially launched in 2001, it could produce 385 brake hp (bhp) and 385 lb-ft of torque. In 2002, this engine was modified to deliver 405 bhp and 400 lb-ft of torque.

Initially Used in the High-performance Chevrolet Corvette C5 Z06 2001-2004

This engine was initially used in the high-performance Chevrolet Corvette C5 Z06 from 2001 to 2004. Later, it was used in the Cadillac CTS V Series and the SSC Ultimate Aero TT vehicles.

Firing Order

As for the firing order of the LS6 engine, it is also 1-8-7-2-6-5-4-3.

Generation 4 Chevy Engines

Actively Manufactured Between 2005 and 2020

The fourth-generation engines were actively manufactured between 2005 and 2020. It was intentionally designed to have provisions for high displacement ranges with a maximum of 7,441 cubic capacity (cc) and deliver a power output of 776 bhp.

Based on the Design of the Third Generation Category

This engine category was, of course, based on the design of the third generation category. Its design took into consideration displacement on demand. It is a technology allowing cylinders in the firing order to deactivate alternately. Also, it is capable of accommodating variable valve timing.

Chevy LS2 Firing Order

Launched as the New Base Engine for the 2005 Chevrolet Corvette

Initially, the LS2 engine was launched as the new base engine for the 2005 Chevrolet Corvette. It delivers 400 bhp and 400 lb-ft of torque at 6,000 rpm and 4,400 rpm, respectively, from a slightly higher displacement of 5,967 ccs.

Features an Improved Torque Throughout the RPM Range

In essence, it is the same as the high-performance LS6 engine. It’s just that the LS2 features an improved torque throughout the rpm range. The LS2 and LS6 engines use the 243 casting heads, but the former uses it with sodium-filled valves.

Features a Smaller Camshaft

The LS2 engine features a smaller camshaft, and an added 290 cc or 18 cubic inches. Its compression increased to 10.9:1, whereas the LS1 only had 10.25:1 and the LS6 only had 10.5:1.

Basis of the NASCAR Specification Engine

In 2006, this engine was the basis of the NASCAR Specification Engine used in the Camping World Series East and West Divisions of NASCAR as an optional engine.

Chevrolet Vehicles Equipped with LS2 Engines

The Chevrolet vehicles equipped with LS2 engines include the following:

  • 2005 – 2007 Chevrolet Corvette
  • 2005 – 2006 Chevrolet SSR
  • 2006 – 2009 Chevrolet TrailBlazer SS

Similarly, the Chevy LS2 firing order is 1-8-7-2-6-5-4-3.

Chevy LS4 Firing Order

Part of the Fourth Generation Block

The Chevy LS4 engine is part of the fourth generation block. It features 3.78 inches bore blocks and has 5,327 ccs. It features a similar displacement as the Vortec 5300 LY5 engine.

Has an Aluminum Block

But instead of iron, the LS4 has an aluminum block. At the same time, it uses a similar cylinder head casting as the third generation of the LS6 engine.

Adapted for Transverse Front-wheel-drive Applications

Chevy adapted the LS4 engine for transverse front-wheel-drive applications. It features a bell housing bolt pattern distinct from rear-wheel drive blocks.

Chevrolet Vehicles Equipped with the LS4 Engine

The Chevrolet vehicles equipped with the LS4 engine include the following:

  • 2006 – 2009 Chevrolet Impala SS
  • 2006 – 2007 Chevrolet Monte Carlo

Firing Order

As for the Chevy LS firing order, it is 1-8-7-2-6-5-4-3.

Again, what is Chevy’s firing order? The Chevy LS engines’ firing order is 1-8-7-2-6-5-4-3, which differs from SB or BB V8 engines. This is for a standard cross-plane crankshaft in which the throws are spaced 90° apart and a standard firing order camshaft.

Chevy LS7 Firing Order

Has a Modified Block

The Chevy LS7 is another type of engine patterned after the fourth generation architecture, which has a 7,011 cc. Its block is modified, featuring sleeved cylinders in an aluminum block.

Larger and Longer Bore and Stroke

The bore and the stroke are larger and longer than the LS2 engine at 4.125 inches and 4 inches. In terms of bore spacing, it is retained at 4.4 inches. But this time, the engine requires pressed-in cylinder liners.

Chevy Vehicles Equipped with the LS7 Engine

The Chevy vehicles equipped with the LS7 engine include the following:

  • 2006 – 2013 Chevrolet Corvette Z06
  • 2014 – 2015 Chevrolet Camaro Z/28

Firing Order

Like other LS engines, the Chevy LS7 firing order is also 1-8-7-2-6-5-4-3.

Chevy LS3 Firing Order

small block chevy firing order

Initially Launched as the New Base Engine of the 2008 Chevrolet Corvette

The LS3 engine was initially launched as the new base engine of the Chevrolet Corvette for its 2008 model. It delivers 430 bhp and 424 lb-ft of torque at 5,900 rpm and 4,600 rpm. This engine is certified by the Society of Automotive Engineers (SAE) and does not have the optional Corvette exhaust.

Chevrolet Vehicles with LS3 Engine

This engine features 4.06 inches bore blocks, and the Chevrolet vehicles equipped with this engine are the following:

  • 2008 – 2013 Chevrolet Corvette
  • 2010 – 2015 Chevrolet Camaro SS
  • 2014 – 2017 Chevrolet SS

Firing Order

The Chevy LS3 firing order is also 1-8-7-2-6-5-4-3.

Chevy LS9 Firing Order

Supercharged 6,162 cc Engine Patterned on the LS3

As for the Chevy LS9, it also forms part of the Gen 4 category. It is a supercharged 6,162 cc engine patterned on the LS3.

Chevy did not pattern it after the LS7 because of the higher cylinder pressures resulting from the supercharger. The higher cylinder walls of the LS3 are more appropriate to use.

Installed in the 2009-2013 Chevrolet Corvette ZR1 Models

This engine was in the 2009 – 2013 Chevrolet Corvette ZR1 models. The Chevy LS9 firing order is also 1-8-7-2-6-5-4-3.

Chevy LS5 Firing Order

Features a Standard Cast-iron Block and a Forged Steel Crankshaft

The LS5 engine features a standard cast-iron block and a forged steel crankshaft with five main bearings. It delivers 360 hp.

Chevy Vehicles with LS5 Engine

Some of the Chevy vehicles that were once equipped with the LS5 engine were the Chevrolet Corvette, the Chevrolet Camaro, and the Chevrolet Chevelle.

Firing Order

The Chevy LS5 engine does not belong to the third and fourth generations. Nonetheless, its firing order is also 1-8-7-2-6-5-4-3.

Is There Any Benefit in Performing a 4/7 Swap on an LS Engine

List of Theoretical Firing Orders for an LS Engine

Here is a list of theoretical firing orders for an LS engine featuring a cross-plane crankshaft:

  • 1-5-4-2-6-8-7-3 LLRRRRLL
  • 1-5-4-3-6-8-7-2 LLRLRRLR
  • 1-5-7-2-6-8-4-3 LLLRRRRL
  • 1-5-7-3-6-8-4-2 LLLLRRRR
  • 1-8-4-2-6-5-7-3 LRRRRLLL
  • 1-8-4-3-6-5-7-2 LRRLRLLR
  • 1-8-7-2-6-5-4-3 LRLRRLRL
  • 1-8-7-3-6-5-4-2 LRLLRLRR

L and R Meaning

The L and R refer to which bank each cylinder belongs to in the firing order.

The standard LS firing order is 1-8-7-2-6-5-4-3. In essence, this firing order indeed does a great job of alternately firing between banks as much as possible.

4/7 Swap Meaning

However, there is this popular modification known as the 4/7 Swap. This method switches the firing order of cylinders 4 and 7. Interestingly, all four cylinders on a single bank are firing in succession. Then, it is followed by the remaining cylinders on the other bank.

Some say that with the 4/7 Swap, there is only a minor improvement in power/torque output. But some say otherwise. Some sources say that the Corvette team won in a Daytona race using this 4/7 swap firing order.

4/7 Swap Original Firing Order

However, the 4/7 Swap is a modification on Gen I and Gen II small block and big block Chevy engines. Their original firing order is 1-8-4-3-6-5-7-2.

On the other hand, the firing order of the LS series engine already encompasses the 4/7 Swap. The engineers of General Motors have figured out the benefits of this modification. So, they incorporated it into the 3rd Gen small block engine when designing it.

Frequently Asked Questions – Importance of Chevy LS Firing Order

Here are several frequently asked questions about the importance of the Chevy LS firing order:

Why Is Engine Firing Order Important?

The correct firing order in an engine results in minimum vibrations in the system. This results in a smooth ride and adds comfort to both the driver and the passengers.

Do All LS Engines Have the Same Firing Order?

The firing order of LS Series engines is different from the firing order of early small block and LT1 engines. The engine firing order has swapped cylinders 2, 3, 7, and 4.

What Is the Firing Order on a 5.3 Chevy Engine?

The firing order on a 5.3 Chevy engine is 1-8-7-2-6-5-4-3. This is the same as the firing order on the 4.8L, 6.0L, and 8.1L engines.

What Is the Firing Order of an LS?

The standard firing order on an LS engine is 1-8-7-2-6-5-4-3, and it does a decent job of firing alternately between banks. There is also this so-called 4/7 Swap that switches the firing order of cylinders 4 and 7. It is said to improve the performance of the engine.

In Closing: Chevy LS Firing Order

Again, the Chevy LS firing order is 1-8-7-2-6-5-4-3. This is for a standard firing order camshaft and a standard cross-plane crankshaft in which the throws are spaced 90 degrees apart.

It is an upgrade on the firing order of Chevy vehicles’ traditional Small/Big Block engines. This firing order does an excellent job of firing alternately between banks.

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