5 facts about General Motors LT6 V8


The next installment of the Chevrolet Corvette Z06 is just around the corner, and its engine is a love letter to internal combustion.

Dubbed Gemini, this naturally aspirated, DOHC 5.5-liter V8 produces enough power to launch the next ‘Vette in low Earth orbit. This engine (code name LT6) makes the Z06 the most powerful naturally aspirated V8 production car in the world, with 670 hp on tap, with 460 lb-ft of torque.

that surpasses the legendary The 6.3-litre V8 in the Mercedes-Benz SLS AMG Black Series which produced an impressive 622 hp. There’s more to this engine than just numbers, though, so let’s dive in.

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It’s still a small block… even without tappets

Chevrolet’s marketing department probably didn’t know what was on their hands when they launched the first advertisements for their New Turbo Fire V8 for 1955. The all-new car might have been the focus of the team, but that 265 CID pushrod V8 was the real star.

Now in its fifth generation, it’s hard to ignore the presence of the small block in the Chevy lineup. But purists might not consider the Gemini engine a member of the small-block family: the flat-plane crankshaft gives it a unique firing order, and the overhead camshaft design throws the push rods from the small block to the trash.

Also according to the team that developed the engine, this 5.5-liter DOHC V8 carries the small-block badge and the famous 4,400-inch bore spacing. A 5.5-liter engine is compact by Corvette standards. The last time a smaller engine was found under its hood was the L30 327 CID (5.4 liter) V8 in 1969 in the C3, rated at 300 hp.


Gemini Rockets – Come Build Your Own!

The team behind the new Z06 engine had fun giving it a name: Gemini, like in the rockets that put Americans in spaceas well as astronauts in corvettes. As a tribute, General Motors powertrain engineers planted 54 tiny rockets on engine castings and forgings as Easter eggs to discover while ripping in the garage or building one yourself at the Bowling Green, Ky. plant’s Performance Build Center.

Yes, you can buy a Z06, drive to the factory and build your engine by hand (supervised by a specialist), then have your name prominently displayed on a small plaque that will be clearly visible when the hood is open.

Although it is not said explicitly, it seems that the number of rockets might be an homage to 1954, the year Chevrolet’s legendary small-block V8 hit the road as 1955 model year cars. That might just be a coincidence, but a briefing of three hours with the engineering team this week suggests they didn’t do anything by accident.


Race tested, production approved

It took a long time for this clean sheet engine program to be fully cooked – development started in 2014. But when you realize this engine made its first roars behind the C8.R riders. racing car, this cycle makes more sense.

Although the race engine and the road engine do not contain the exact same parts, there has been more than a little information exchanged. Both engines share the same design basis and the same aluminum cylinder block and cylinder heads, as well as the valve system and the fuel system.

Obviously, the packaging, tuning and exhaust note of the two engines are completely different. The Z06 is meant to be a semi-everyday rider, while the hair-raising 8600 rpm redline guarantees good times on the track. Another fun fact: the LT6 has five camshafts – four to govern the valve train and a short fifth cradled in the valley with two lobes to drive the fuel pump.


Solid valvetrain without service

Anyone who knows a solid, mechanical valve knows that resetting and checking valve clearance, the distance between the tip of the rocker arm and the valve stemisn’t just part of maintenance, it’s a way of life.

Well, Chevrolet’s latest V8 has a finger-follower valve train that currently does not expect to adjust valve clearance. Before heading to its Corvette home, the engine has its valve clearance checked Three times during the assembly process.

Engineers applied a diamond-like carbon coating to the finger followers that operate the valves (titanium on the intake side, sodium nitrided filled for the exhaust), and each finger has an integrated oil jet for targeted lubrication.

During endurance testing, the team saw no significant wear on these parts, at least not enough wear to affect valve clearance. GM claims that no maintenance interval is required. However, since these engines are in the hands of the public, anything is possible.


Ferrari 458 inspired

Benchmarking is a tool in almost all the automaker’s arsenal, especially when you’re starting from scratch. The process reveals what is successful, or a feature you like, and whether your hardware is compatible.

When it comes to naturally aspirated supercars, the Ferrari 458 was king, and the team behind this Gemini V8 wanted to take a look at the 4.5-liter V8 and see how Maranello works.

The team went to e-Bay, found a wrecked Ferrari 458 in Poland, and sent a check for $25,000 for the engine – and it was actually shipped to GM’s powertrain operations in Pontiac, Michigan! It’s hard to say exactly how the 458’s engine inspired the engineering team, but there might be a hint of Italian flair in this radical American V8.

—with Tom Murphy

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