Performance Chevy LS Engine Comparison - LS Motors Decoded

The Ultimate Guide To Every Gen III And IV Small-Block Ever Built

Stephen Kim Dec 1, 2009 0 Comment(s)

LS9
The big hoss in LS land, at least for the moment, is the factory-supercharged 638hp small-block that powers the new Corvette ZR1. Not only is the Gen IV LS9 the most powerful engine ever conceived by GM, it easily produces the fattest torque curve of any Chevy in history. While its torque peak of 604 lb-ft at 3,800 rpm is very impressive, the fact that it belts out 350 lb-ft at just 1,000 rpm is downright breathtaking. At its core, the LS9 shares more in common with the LS3 and L92-found in base Corvettes and Cadillac Escalades, respectively-than the LS7. To enhance block rigidity, GM passed on the LS7's 4.125-inch bore dimensions for the thicker cylinder walls afforded by smaller 4.065-inch holes. Furthermore, the block is cast from 319-T7 aluminum and features larger bulkheads, which makes it substantially stronger than prior LS units. It encases a steel crank, titanium rods, and forged 9.1:1 pistons. With a remarkably efficient 2.3L Eaton blower huffing out 10.5 psi through a dual-core intercooler, the exotic race-ported 12-degree LS7 cylinder heads were deemed unnecessary. Instead, GM opted for 15-degree rectangle-port castings that are very similar in design to the L92 and LS3 heads, but built from more durable A-356T6 aluminum. Sometime this summer, GM Performance Parts will start selling complete LS9 crate motors (PN: 19201990) for about $22,000. Granted that isn't cheap, it's still a heck of a lot less than trying to replicate a motor of this caliber that's also emissions legal and capable of lasting 100,000 miles. Moreover, the rugged LS9 block will certainly be a popular foundation for LS stroker buildups once it's released.

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LSA
Think of the LSA as the LS9's detuned little brother. Even so, the LSA's 556 hp and 551 lb-ft have helped make the '09 Cadillac CTS-V the quickest four-door sedan to ever lap Germany's famed Nurburgring road course. Major differences between it and the LS9 are the use of hypereutectic pistons instead of forged slugs, and powdered metal connecting rods instead of titanium units. While the LSA also utilizes an Eaton blower, it's slightly smaller at 1.9L, and produces 1.5 fewer psi of boost. It's a very impressive setup, indeed, but the limited production numbers of Cadillac's top dog means there will be very few LSA's to extract from your local boneyard.

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