Chevrolet Gemini small-block engine

Gemini small-block engine
Overview
ManufacturerGeneral Motors (Chevrolet)
Production2022–present
Layout
Configuration90° V8
Displacement5,463 cc (333.4 cu in)
Cylinder bore104.25 mm (4.104 in)
Piston stroke80 mm (3.1 in)
Cylinder block materialSand-cast A319 Aluminum
Cylinder head materialAluminum
ValvetrainDOHC 4 valves
Compression ratio
  • 12.5:1 (LT6)
  • 9.8:1 (LT7)
RPM range
Max. engine speed8,600 RPM (soft), 9,000 RPM (hard)
Combustion
TurbochargerTwin-turbo (LT7)
Fuel system
ManagementGM E68 (32-bit)
Fuel typeGasoline
Oil systemDry sump
Cooling systemWater-cooled

The Chevrolet Gemini small-block engine is a dual-overhead cam (DOHC) V8 engine designed by General Motors. While technically a small-block engine because of its bore spacing of 4.4 inches,[1][2] General Motors engineers do not consider it to be a part of the traditional Chevrolet small block lineage because of the substantial reworking, specialized development, and unique technical features distinguishing its design.[3][4][5]

The Gemini is a clean-sheet design, mechanically unrelated to both the LS-based engines and the Cadillac Blackwing V8. Its most notable traits include a flat-plane crankshaft and dual-overhead camshafts, which represents a departure from the traditional pushrod valves and crossplane crankshafts found in all previous generations of Chevrolet small-block engines. As of July 2024, the Gemini engine has two variants, dubbed LT6 and LT7.[6]

LT6

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The LT6 is a 5.5-liter, naturally-aspirated V8 engine. It debuted in the eighth-generation Corvette Z06, and was unveiled on October 26, 2021.[1]

While the LT6 features a redline of 8,600 RPM, it generates a maximum of 670 hp (500 kW; 679 PS) at 8,400 RPM and 460 lb⋅ft (624 N⋅m) of torque at 6,300 RPM. These figures make it the most powerful naturally-aspirated production V8 engine of all time; the engine to previously hold this title, the Mercedes-Benz SLS AMG Black Series M159 6.2-liter V8, made 622 hp (464 kW; 631 PS) at 7,400 RPM. [7][8][1]

The LT6 is also the largest flat-plane V8 used in a production car by displacement, dethroning the Ford Voodoo. This is notable due to the additional vibrations inherent to this architecture compared to a crossplane V8, which tend to scale up with displacement.[9]

A modified version of the LT6 has powered the Chevrolet Corvette C8.R since 2019, and many features in the racing engine carry over to the road engine.[2] Other notable features include a cast aluminum block, dual coil valve springs supporting titanium intake & sodium filled exhaust valves, forged aluminum pistons, forged titanium connecting rods, active split intake manifold with twin 87mm throttle bodies, four-into-two-into-one stainless steel exhaust headers, and a factory six-stage 10-quart dry sump oiling system with individual crank bay scavenging.[1]

Applications:

Year(s) Model Power Torque Dyno Chart
2023–present Chevrolet Corvette Z06 670 hp (500 kW) @ 8400 rpm 460 lb⋅ft (624 N⋅m) @ 6300 rpm link

LT7

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The LT7 is a twin-turbocharged variant of the LT6 which debuted in the eighth-generation Corvette ZR1 and was unveiled on July 25, 2024. The LT7 has a redline of 8,000 RPM, generating 1,064 hp (793 kW; 1,079 PS) at 7,000 RPM and 828 lb⋅ft (1,123 N⋅m) of torque at 6,000 RPM.

Although it was released later, the LT7 was developed in tandem with its LT6 sibling. Compared to it, the LT7 has stronger pistons and connecting rods. Combined with the bigger combustion chamber on the heads, this lowers the compression ratio from 12.5:1 to 9.8:1. Unlike the LT6, the LT7 uses both direct fuel injection and port injection, with a total of 16 injectors. However, the block casting is identical, and the crankshaft is almost identical. The turbochargers produce up to 20 psi (1.4 bar) in normal operating conditions and a maximum of 24 psi (1.7 bar) under high temperatures. Other features specific to the LT7 include turbo-integrated exhaust manifolds, water-to-air intercoolers, and an electrically actuated wastegate.[10][6]

Applications:

Year(s) Model Power Torque
2025–present Chevrolet Corvette ZR1 1,064 hp (793 kW) @ 7000 rpm 828 lb⋅ft (1,123 N⋅m) @ 6000 rpm

See also

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References

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  1. ^ a b c d Steven Rupp (October 26, 2021). "Flat-Plane Crank DOHC LT6 to Power the 2023 Corvette Z06! Details and Specs". motortrend.com. Retrieved October 27, 2021.
  2. ^ a b "2023 CHEVROLET CORVETTE Z06 ELEVATES THE AMERICAN SUPERCAR". media.chevrolet.com. October 26, 2021. Retrieved October 28, 2021.
  3. ^ Joe Kucinski (February 18, 2022). "LT6 Engine Deep Dive: Everything You Need to Know about the Corvette Z06 Flat-Plane-Crank V8". corvetteforum.com. Retrieved March 5, 2022.
  4. ^ Wren, Wesley (February 18, 2022). "5 Fast Facts About Chevrolet's LT6: The Corvette Z06's Heart". AutoWeek.
  5. ^ Kelly, Iain (October 28, 2021). "The LT6 V8: Inside GM's most powerful small-block". Street Machine. WhichCar.
  6. ^ a b Tingwall, Eric (July 25, 2024). "Monster! The Story of the Corvette ZR1's LT7 V-8 Engine and How It Makes 1,000+HP". MotorTrend.
  7. ^ Markus, Frank (October 26, 2021). "How the C8 Corvette Z06's LT6 Became the World's Most Powerful Naturally Aspirated Production V-8". MotorTrend. Archived from the original on October 26, 2021.
  8. ^ Colwell, K.C. (October 26, 2021). "2023 Chevy Corvette Z06 Brings 670 HP of Naturally Aspirated Fury". Car and Driver. Archived from the original on October 26, 2021.
  9. ^ Sommers, Alex (September 7, 2021). "Chevy's eighth-gen Corvette Z06 is poised to topple these 3 production-car V-8 records".
  10. ^ Stafford, Eric (July 25, 2024). "2025 Chevy Corvette ZR1 Has 1064 HP and Is Poised to Slay Supercars". Car and Driver.
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