C8 Z06 Reliability — Will the LT6 Yield Triumph or Tragedy?

As the foundation of the C8 Z06, what scares you most about the new LT6?

Ed.Note: Please welcome Andrew Nabors to the CorvetteForum editorial team. He’s owned five Corvettes since 1998 and has worked at Eckler’s as well as duPont Registry. His current fleet includes an ’02 SS Camaro (original owner) with heads/cam/converter along with an ’04 CTS-V with heads/cam. Other rides include an ’05 Avalanche (original owner) and an ’05 Ranier 5.3 “FailBlazer.”  Today we’ve asked him to write about the 2023 Corvette Z06’s new 5.5L LT6 flat-plane-crank V8.

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What comes to mind when you hear “solid lifters” and “flat-plane crank?” Nervous laughter aside, Bowling Green is entering uncharted territory. Yesterday, I stumbled across a great CorvetteForum thread posted by Vito.A discussing potential shortfalls in the LT6’s rods and valves. Namely, the wristpins don’t have bronze bushings and the two-piece exhaust valves remind us of the C6Z fragility.

Let’s take an objective look at this. The LS7 made great power, but it was not even close to what Katech built for the C6R. Meanwhile, the LT6 has seen action in the C8.R and brought home the checkered flag. GM can’t afford to screw this up, as it will be the last great V8.

Shaky Situation

Before the Nashville Auto Show in 2019, Brown Lee Ford gave me a GT350 for the weekend. Yes, it shakes at idle. Every Italian V8 does, it’s just the nature of the flat-plane crankshaft. You learn quickly to keep RPMs above 3,000 to avoid it. Honestly, a little wobble is okay given such power.

When I worked at Eckler’s, I lived around the corner from Lake X. This is where validation of the LT5 took place. Mercury Marine’s Florida hideaway is used to test each engine to destruction. Overhead cams are not to be feared, but what about the valvetrain?

Solid Foundations

The LT6 boasts solid cam followers. Essentially, they serve the purpose of a lifter on overhead cams. The advantages are numerous, with high-rpm being paramount. For example, the COPO Camaro redlines at 8,500, making power all the way.

However, historically speaking, the traditional downside to a solid valvetrain is adjusting them every few months. The worst example has to be the E46 M3. (Hooray, German Precision.) GM wants to avoid this type of service schedule and claims the LT6’s lifters are “set for life.” Which, of course, should draw scrutiny from cautious consumers.

According to the engineers, the valve lash is 3D scanned to select the optimal shim and you will never need to pull the covers. It is standard procedure to check and adjust valves on many modern cars. Cosworth has done this with Aston-Martin V12 engines, offering a service interval of 60,000 miles. Having overhead cams makes it more difficult, but it’s not hard if you have a few hours. It won’t be long before aftermarket cams will have it making 700 hp anyways.

Here’s What Actually Scares Me about the LT6

At the end of the day, LT6 internals don’t scare me. But here are a few things that do.

Not only is the fuel rail under the headers, it’s pressurized to 5,076 psi. Aside from fire concerns, let’s hope vapor lock doesn’t say hello. Also, the nature of direct-injection causes soot to build up inside the heads and intake. With three radiators and two gallons of 5W-50, it will take a while to warm up. During this time, an incremental amount of sludge could form inside the heads. It will take a few minutes for the oil to get deep into the tiny spaces, so we hope the computer-selected shims are on-point.

Speaking of which, how do you drive your Corvette? Because the LT6 incorporates Italian-style internals, we’d venture to guess that it will need occasional flogging to stay happy. (Hello, Italian tune-up.) In other words, treat it like a track-day champion and reap the rewards. But drive it like an NCRS member and be remembered for nothing. Didn’t we learn anything from the sinkhole? So, aside from the low-speed vibrations, you have another reason to drive it like the engineers intended.

Lastly, should we talk about how each LT6 cylinder head has its own fuel pump? Like a blast from the past, we see two fuel delivery systems share the same manifold. The last time this happened was the 1982-84 CrossFire, better known as cease-fire. And, yes, this is all in good humor, as nothing will ever be that bad again.

Remember, GM benchmarked the Ferrari 458, and it has proven to be one of the brand’s most reliable models. We have a lot to look forward to here!

That’s my take on it, let’s hear it from you!

Photos: Engineering Explained

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