Sign up now to join the JEGS email newsletter and be the first to learn about new products, special deals and e-mail only offers!
![](https://www.jegs.com/tech-articles/wp-content/uploads/2024/06/email_signup2.jpg)
Are you considering an LS engine swap for your custom project? One of the first choices you’ll need to make is whether to go with a Gen III or a Gen IV LS engine.
Both generations share a similar foundational design dating back to 1997, and are wildly popular today with gearheads and automotive enthusiasts for their robust build and extensive upgrade potential.
Still, there are some key differences that may sway your decision. Whether you're building a street machine, a track day car, or simply looking to breathe new life into an old classic, understanding how these engines differ will help you maximize your project’s potential.
Thankfully, this article covers everything you need to know about these GM small-block motors, allowing you to confidently choose the best option to match your performance goals.
Let’s get started.
General Motors' LS engine series first debuted in 1997 in the C5 Corvette, continuing the automaker's earlier Gen I and Gen II small-block designs.
The first LS engine, dubbed the Gen III LS, was produced from 1997 to 2007 and featured a 24x crankshaft trigger wheel and a cam sensor mounted at the rear of the camshaft. These engines were known for their robustness and versatility, offering a solid foundation for performance enhancements.
In 2005, GM started transitioning to the Gen IV LS engines, introducing key upgrades such as a 58x crank trigger wheel and relocating the cam sensor to the timing chain cover. These changes improved engine timing accuracy and overall performance.
The Gen IV engines also included advancements like Variable Valve Timing (VVT) and Active Fuel Management (AFM), later evolving into Dynamic Fuel Management (DFM). This allowed for improved fuel efficiency by enabling the engine to operate on fewer cylinders under certain conditions. It's important to consider these features when modifying your engine, as many enthusiasts opt to disable systems like AFM for consistent performance across all cylinders.
Both Gen III and Gen IV engines maintained the traditional small-block V8 configuration but with improvements in materials and design. They featured aluminum blocks and heads, deep skirt blocks with cross-bolted main caps, and advanced airflow systems.
This combination of legacy design elements and modern technological advancements made the LS series a popular choice for high-performance and custom automotive applications.
Sign up now to join the JEGS email newsletter and be the first to learn about new products, special deals and e-mail only offers!
While both the Gen III and Gen IV LS motor options make fantastic platforms for upgrades, there are some key differences you’ll want to take note of to ensure your performance goals are met.
Below we’ll detail how these engine’s specs differ:
Now that you better understand the differences between the Gen III and Gen IV LS engines, let’s review the 5 best upgrades to consider for noticeable power gains:
That’s a wrap folks, a complete rundown on Gen III and Gen IV LS engine upgrades. No matter your choice, both LS motors make versatile and robust platforms for performance upgrades and are sure to result in some good times.
For all your automotive needs, consider JEGS, a leading supplier of performance auto parts. Browse our massive selection of parts online and have your products sent straight to your garage. Still have questions? Contact our team today.