Identifying Gen 3/4/5 Chevrolet Engines
In this guide we will be covering engine designations for generation 3, 4, and 5 Chevrolet product engines. This will cover the release of the LS1 in 1997 and go to today’s Gen 5 LT7 in 2024. We have grouped these by generation and provided a brief explanation of what each engine code means to help inform you about what engine you want or have. Before diving into each engine code, it’s important to first understand the difference between the engines that came in cars, and trucks, and the different types of cylinder head port offered on these engines and what it means for performance and compatibility.
LS and LT vs Vortec
The “LS” or “LT” moniker refers specifically to aluminum construction engines that came in Chevrolet cars. So, when someone is referring to an LS1/LS2/LS6, LS3, or LS7, they mean all aluminum (including the block itself) engines found in Corvettes, Camaros, GTOs, Caprices, etc. “Vortec” is the name for Gen III and IV engines that were used in Chevrolet trucks. These Vortec engines, in Gen III, were exclusively iron blocks with aluminum heads. “What about the L33!?” I hear you cry - don’t worry, we’ll cover that later. It’s technically Gen 3.5. Thanks, GM. In Gen V, the truck engines became known as the EcoTec, instead of the Vortec.
Cylinder Head port styles
Chevrolet engines in Gen III and Gen IV use three types of cylinder head port styles; cathedral, small rectangle port, and large rectangle port. In Gen V, all of the ports are (currently) the same, but where the intake bolts down is in different locations depending on what type of LT you have. The graphic below shows the visual differences, as well as what engines use what port style, helping to identify what heads can fit on what engine and what intake manifolds are cross-compatible. This is why you often see LS1/LS2/LS6 grouped together, while LS3 is unique and LS7 is unique.
Gen III engines (1997-2005)
Gen III engines were the first release of Chevrolet’s new architecture for SBCs, which they began developing it in 1993. They were produced from 1997 through 2005, with the 1997 Corvette officially debuted the LS1, marking the beginning of Gen III.
LS1 - 5.7L aluminum
LS6 - 5.7L aluminum
LR4 - 4.8L iron
LM7/L59 - 5.3L iron
LM4 - 5.3L aluminum version of the LM7, only produced from 2003-2005.
LQ4/LQ9 - 6.0L iron
L33 - 5.3L (This is the Gen 3.5, aluminum 5.3 that is an oddball. It still has the 24X reluctor wheel, which is a Gen III specific feature, but it did have some Gen IV components)
LS2 - 6.0L aluminum with a Gen IV block but a 24X reluctor. While “technically” Gen IV, we consider the LS2 to be Gen III due to the reluctor wheel.
Gen IV engines (2005-2013)
Gen IV engines were sort of phased into use, as there was a cross over point where some Gen III engines, such as the LS2, L33, etc began to incorporate Gen IV developments before an official Gen IV engine was released. The first Gen IV engine in our books is technically the LS7, which debuted in, once again Corvettes, in 2006. The LS7 was the first 58X reluctor wheel engine, and used an E38 ECU.
LS7 - 7.0L aluminum featuring titanium connecting rods, titanium intake valves, and 1.8 ratio rockers. You could also purchase the LS427, which was only available as a crate option, but converted the LS7 from dry sump to wet sump and included a higher lift camshaft.
L76/L77/L98 - 6.0L aluminum, the L76 introduced AFM (active fuel management) but for Holden, which did not use AFM, GM removed redundant hardware and called it the L98. The L77 is the same as the L76, but has flex-fuel capability.
LY6/L96 - 6.0L iron, the L96 is flex fuel capable while the LY6 is not.
LFA/LZ1 - 6.0L aluminum, these are more rare and came in Hybrid GM vehicles. The LZ1 is the same as the LFA, but came with AFM and VVT.
LY2/L20 - 4.8L iron, the LY2 does not have VVT while the L20 does.
LY5/LMG/LMF - 5.3L iron, with the LMG having flex fuel compatibility and VVT from 2010 on. The LMF Is a low-tech LY5, but it does have VVT.
LH6/LH8/LH9/LC9 - 5.3L aluminum, with the LC9 and LH9 having flex fuel compatibility and VVT from 2010 on. The LH9 also had VVT.
LS4 - 5.3 aluminum for FWD vehicles, meaning it has a different bellhousing pattern and a shorter crankshaft.
L92/L9H/L94 - 6.2L aluminum with the L9H having flex fuel capability, and the L94 having AFM.
LS3/L99 - 6.2L aluminum, the L99 is a smaller cam LS3 with AFM and VVT.
LSA - 6.2L aluminum factory supercharged engine with a smaller blower than the LS9, lower compression, and cast pistons because it was designed for Cadillac and Cadillac didn’t like the piston slap of forged pistons.
LS9 - 6.2L aluminum factory supercharged engine found in the C6 ZR1 from 2009-2013.
Gen V engines (2014 - Present)
The Gen V Chevrolet engines were introduced alongside the release of the C7 Corvette, with the LT1 being the first to debut. GM changed a significant amount of the architecture for Gen 5, correcting and improving some issues found in the Gen III/IV design, and creating new challenges as well. One of the biggest changes to mark the arrival of Gen V was the conversion to direct injection. Most Gen V engines transitioned to aluminum, they converted to electronic power steering (meaning there is no power steering pump on the accessory drive anymore, making swaps harder) and there is a mechanically-driven high pressure pump driven off the rear of the camshaft to support the direct injection. Due to this additional, the 12 o’clock bell housing bolt hole was slightly relocated, meaning LS bell housings are not compatible. Additionally, all Gen V crankshafts are 8 bolts, not 6 bolt like most LS engines meaning clutches and flywheels do not interchange.
LV3/LV1 - 4.3L aluminum V6! There were no generation III or IV V6 engines based on the small block V8 design. The LV1 did not have AFM.
L82/L83/L8B/L84 - 5.3L aluminum EcoTec (replacing Vortec for truck engines) . The L8B is a hybrid version, while the L82 uses AFM and the L84 uses DFM (dynamic fuel management) which can alternate between 17 different firing orders.
LT1 - 6.2L aluminum
LT2 - 6.2L aluminum found in the 2020 C8, it is designed for mid-engine placement and is dry sump.
L86/L87 - 6.2L aluminum EcoTec (replacing Vortec) modified LT1 for truck use. The L86 had AFM, but the L87 advanced to DFM.
LT4 - 6.2L aluminum factory supercharged engine including stronger aluminum heads, titanium intake valves, forged rods, forged pistons, an aluminum balancer, and dry sump.
LT5 - 6.2L aluminum factory supercharged engine for the C7 ZR1. It features port injection on top of the direct injection to support upper-RPM fuel demands.
L8T - 6.6L iron, and so far the only iron block in the Gen V lineup. It has a longer stroke crankshaft and lower compression for the heavy duty truck market.
LT6 - 5.5L aluminum factory supercharged engine for the C8 Z06. The LT6 is a wildly different design than any previous GM V8, featuring a flat plane crankshaft, a 2-piece block(!) consisting of the block casting and a lower crankcase casting. The LT6 is also DOHC, meaning dual overhead camshafts, as opposed to the usual pushrod V8 design.
LT7 - 5.5L aluminum factory twin turbocharged engine for the C8 ZR1. The LT7 also features the flat plane crankshaft, 2 piece block, and DOHC of the LT6, but has differentiating factors in the internals and cylinder heads. The LT7 also takes after the LT5 by adding port injection on top of the direct injection to support the 2 gallons per minute fuel draw of this engine at wide open.
So, what is the best LS engine?
The best LS engine is the one that you already have, the one that fits your budget, the one whose name you think sounds the coolest, or the LS9 (we might be biased). In reality the “best” LS engine is a loose concept. We believe that the architecture of these engines is extremely impressive, and the modular nature of the LS coupled with the ridiculous amount of aftermarket support really means that your options are endless. Do you want LS7 heads on your LS3 that is stroked to a 6.8L? Do you want a 14:1 compression 5.3 with LS2 heads on e85? Do you want a 400 horsepower LS engine or do you want a 2500 horsepower LS engine? Do you want to RPM your engine to 6,000, or to 11,000?
At Flag Motorsports, we spend a lot of time with our clients to understand what their goals are for their engine, and how they will be using the car the engine is going in. We work carefully to come up with combinations and engine packages tailored to their needs. If you’re interested in discussing an LS engine, or wondering what LS engine you might already have from the list above, get in touch with us and let’s build an engine!