GM LS9 Vs. LT4 Engine: What's The Difference?

Chevrolet has been making some of the best V8 engines in the world for decades. They've made small blocks and big blocks, a long list of high-horsepower engines, and several of the most reliable V8 engines ever. A testament to their versatility, many Chevrolet engines are used in swaps outside the brand, powering vehicles as unlikely as Miatas or as seemingly antithetical as classic Fords. With all these V8s in its lineup it's important to ask what sets one V8 apart from another.

Two Chevy V8 engines that offer similar power and size are the LS9 and the LT4. They are supercharged 6.2-liter V8s that put out considerable power, and they both powered high-performance versions of the Chevy Corvette, which means they have proper heritage. They're still available as crate engines that you can buy from Chevrolet if you're looking to put big power under the hood of your hot rod. So, what's the difference between these two engines?

The LS9 powered the sixth-generation Chevrolet Corvette ZR1 from 2009 to 2013. While it didn't live under the hood of many cars, it provided big power and an excellent driving experience. The LS9 produces 638 horsepower at 6,500 rpm and 604 lb-ft of torque at 3,800 RPM. In the Corvette ZR1, the LS9 used a Roots-type supercharger and an integrated charge cooling system that reduced intake air temperature. The LS9 was hand-built for the ZR1, a rarity when it comes to mass-market engines.

The LS9 has a compression ratio of 9.1:1 with a max engine speed of 6,600 rpm. The crankshaft, camshaft, and main bearing caps are all made from steel, but the connecting rods are made from forged titanium. The exhaust manifold for the LS9 is stainless steel, while the block, cylinder head, and intake manifold are all cast aluminum. The LS9 in the 2009 Corvette ZR1 was capable of some pretty impressive feats. Chevy listed the car's top speed at 205 mph (the highest for any GM car at the time) and when Car and Driver tested one back in 2009, it went from 0-60 mph in just 3.4 seconds –- a speed that's still respectable compared to the highest-performing sports cars in 2024.

Providing a bit more power and torque, the LT4 was an impressive follow-up to the LS9. Also a 6.2-liter supercharged V8, the LT4 was introduced in the seventh-generation Corvette Z06 in 2015 and it still powers multiple GM products today. Along with the C7 Z06, the LT4 was under the hood of the Cadillac CTS-V sedan (2016-2019) and is still available in the Camaro ZL1 (2017-present), Cadillac CT5-V Blackwing (2022-present), and Cadillac Escalade-V (2023-present). In the 2015 Z06, the LT4 produced 650 horsepower and 650 lb-ft of torque. In the Cadillac Escalade-V, the LT4 puts out even more power — 682 horsepower and 653 lb-ft of torque.

Just like the LS9, the LT4 has a max engine speed of 6,600 RPM. The LT4, however, has a compression ratio of 10:1 and it uses an Eaton supercharger. The LT4's block and cylinder head are both cast aluminum, as is the intake manifold. The crankshaft and camshaft are forged and billet steel, respectively. Both the LT4 and the LS9 use titanium for various parts, including the intake valves in the LT4 and the connecting rods in the LS9. In a Car and Driver test in 2015, the LT4 was capable of rocketing the C7 Z06 from 0-60 mph in just 3.0 seconds — an astonishingly fast time, even by Corvette standards.