LS3 Vs LS7: How The Two Small

Mar 22, 2023

The LS3 and LS7 are undoubtedly one of Chevrolet's most recognized and versatile engines, but which one is the better crate engine?

General Motors introduced the first small-block V-8 in 1954 for the 1955 model year Chevrolets, almost certainly hailed as the best mass-produced V-8 of the time. However, Chevrolet could not have imagined that this compact engine would revolutionize the American automotive industry to ambitious new heights.

The LS series is arguably the most recognized of these beloved small-block engines, thanks to its performance, accessibility, versatility, and durability. These impeccable qualities make the GM LS engine a solid choice for engine swaps, with the LS3 and LS7 rated as the most popular engines in the series.

How do two of the most popular high-performance Chevrolet small-block V-8s compare? We pitted the LS3 and LS7 against each other across several metrics, so read on to find out which one is best for you.

Related: 10 Things We Love About Chevrolet's Biggest And Most Powerful Crate Engine Ever

The LS3 and LS7 engines are part of GM's fourth-generation small-block engine family, alongside the L76, L77, L98, LS4, L99, LS9, and LSA. While they belong to the same generation, the LS7 is the older model than the LS3, produced from 2006 to 2015.

Chevrolet produced the LS7 for the fifth-generation Camaro Z/28 and the sixth-generation Corvette and 427 Convertible. On the other hand, the LS3 featured between 2008 and 2017 in the Camaro SS and C6 Corvette.

The most notable difference between an LS3 and an LS7 is the displacement. The former has a displacement of 6.2 liters (376 cu-in.), while the latter has a larger displacement of 7.0 liters (427 cu-in.).

Interestingly, the LS3 and LS7 have the same 111.76 mm bore center size, but the cylinder bore sizes differ. The LS3 has a bore x stroke of 103.25 x 92 mm, slightly smaller than the LS7's bore x stroke of 104.8 x 101.6 mm.

Related: 10 Reasons Why Chevrolet's LS Crate Engines Are So Special

The LS3 pumps out 430 horsepower with a 5900 rpm redline, while the LS7 delivers 505 horsepower at 6800 rpm. However, with modifications, the LS3's horsepower can peak at 436 horsepower, and on the flip side, the LS7 can go up to 570 horsepower.

The LS7 also provides more torque, rated at 470 lb-ft at 4800 rpm, compared to the LS's 420-428 lb-ft at 4600 rpm. Thanks to the higher output, the LS7 is arguably the most popular option for builders on the market for a racing engine.

Since the LS3 and LS7 come from the same generation of engines, it's unsurprising that they boast similar engine materials. The engine blocks and cylinder heads are made of cast aluminum to ensure the blocks remain lightweight and facilitate higher thermal conductivity. The LS3 and LS7 also utilize composite for the intake manifold and hollow steel for the camshaft.

The LS3 comprises cast nodular iron exhaust manifolds, powder metal main bearing caps, cast iron crankshaft, and forged powder metal connecting rods. On the other hand, the LS7 boasts stainless steel exhaust manifold, forged steel main bearing caps, forged 4140 steel crankshaft, and forged titanium connecting rods.

Besides engine materials, the LS3 and LS7 share similarities in other engine specifications. These include the longitudinal engine orientation, the overhead valve configuration, two valves per cylinder, hydraulic roller valve lifters, an advanced 58X ignition system, advanced electronic throttle control, and the 1-8-7-2-6-5-4-3 firing order.

There are also some notable differences between the two small-block engines. The LS3 has a compression ratio of 10.7:1, while the LS7 has a compression ratio of 11.0:1. Regarding weight, the LS7 is marginally lighter at 454 lbs, compared to the LS3's 466 lbs.

Related: Why A 4-Cylinder LS Crate Motor Would Be Awesome

Further still, the LS3 and LS7 engines provide the same fuel system; a sequential fuel injection configuration. This sequential system ensures maximum efficiency since it allows fuel into the engine through injectors that fire individually, unlike a multi-port system.

According to GM, the LS7 engine must utilize premium fuel featuring a 91 or higher octane level. While the same premium fuel is recommended for the LS3, owners can also choose regular or mid-grade options.

Since General Motors uses the same quality materials to manufacture the LS3 and LS7, they practically have the same reputation regarding reliability. Despite being notably lighter than cast iron engines, the cast aluminum construction allows the LS3 and LS7 to withstand higher thermal conductivity.

And thanks to the efficient engine cooling, the LS3 and LS7 small-block V-8s are generally durable and maintain their strength in the long term. However, a side-by-side comparison reveals that the LS7 has a slight advantage over the LS3 because of its superior performance capabilities.

The LS3 and LS7 are prone to oil pump failure, which results in oil overflow, piston rings grooves that cause knocking noises, and oil pressure issues. LS7-specific problems include cavitation in the oil system and exhaust valves sometimes separating from the stem.

The LS3 is comparatively more problematic than the LS7 since it tends to wear out quicker as mileage increases. Faulty rings are the most complained about, which could lead to higher oil consumption if left unresolved. Additionally, LS3 owners experience valve and lifter issues much sooner than LS7 owners.

Related: The Real Reason GM's LS V8 Engine Has Stood The Test Of Time

Despite GM ceasing production-based manufacturing of these small-block V-8s, willing buyers can still purchase the LS3 crate engine as a remanufactured modern classic. Currently, the LS3 with 430 hp has an MSRP of $10,550, although this price estimate will differ depending on where you purchase the engine and which vehicle it goes into.

Unfortunately, Chevrolet Performance replaced the legendary production-based LS7 with the LS427/570 crate engine with an increased output of 570 hp and 540 lb-ft of torque. But for comparison, the remaining stock of LS-7 has a discounted MSRP of $16,600, still significantly more expensive than the LS-3.

For all their similarities and glaring differences, the LS3 and LS7 small-block V-8s are equally good in what they do. Therefore, it boils down to personal preference when deciding which engine offers the best bang for the buck.

Nonetheless, if you're in the market for a low-budget, high-performance engine for your build, the LS3 is the way to go since the level of performance and maintenance is satisfactory by all means. However, if you have more money in the bank and desire higher power output, the LS7 is the best recommendation.

Simon Kim has always been passionate about machines since childhood, and this has grown into an obsession well into adulthood. As an avid reader and creative content writer, he finds joy and fulfillment in sharing his love for cars and bikes with other machine heads. Currently, Kim seeks to deliver exciting and informative articles on HotCars. He enjoys music and art and dabbles in active sports and virtual gaming in his spare time.