GM is working on the most powerful engine in Holden’s history

Holden showrooms will have a new performance benchmark by 2022 if GM’s Corvette team have anything to do about it.

The new performance hero will be the C8 Corvette Z06, which is the Corvette’s second-in-command in the power wars behind the track-focussed ZR1.

While the Z06 hasn’t been officially confirmed by GM, its production is as inevitable as a GT3 variant for the Porsche 992 911. With the C8 Corvette being produced in right-hand drive from the factory, and being sold in Australia from late-2020, there is a high chance that the Z06 will arrive in Australia – even if it is in extremely limited numbers.

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Power remains speculative for the Z06 at the moment, but the rumour mill is throwing out 600kW and 950Nm as ballpark figures.

Even if those are a drastic overestimation, it would make the Z06 the most powerful thing to ever sit in a Holden showroom

Currently, the HSV converted Chevrolet Camaro ZL1 is top dog in Holden showrooms, with a 6.2-litre supercharged LT4 V8 producing 477kW and 881Nm. This is the same engine found in the C7 Z06 Corvette.

The most powerful Commodore-based product was the HSV GTSR W1, which coincidentally was powered by the dry-sumped LS9 engine from the C6 RZ1 Corvette, rated to 474kW/815Nm.

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The ‘regular’ C8 Corvette Stingray will be rated to 369kW and 637Nm, thanks to its naturally-aspirated 6.2-litre LT2 pushrod V8.

A number of reports have been released in the past week which have given us some pretty significant hints at how the Z06 will produce those staggering figures that would put it amongst the most powerful cars available in Australia outright.

Expected to be codenamed LT7, the engine will be shared with the C8.R race car which will compete in GTE, and it’s here where the details are emerging from.

This is because the C8.R and Z06 will share the same heart, in order to meet GTE regulations. To give the race car the strongest mill possible, the road car will benefit from a pair of turbos and a flat plane crank, according to Motor Trend. Pushrods and superchargers who?

The move to turbos for the C8 is to take full advantage of the ‘Balance of Performance’ regulations that dictate power for GTE, which favours turbocharged engines like those found in the Ferrari 488 and Ford GT.

Motor Trend’s source, which they claim is ‘deep’ within the Corvette’s development team, also drops a nice little hint about the capacity of the engine.

"Everyone thinks it will be a small block, but it won't be," the source is reported as saying. "Listen to the race car."

That would indicate the engine will be larger than the 4.2-litre ‘Blackwing’ that will power Cadillac’s performance flagships.

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Cadillac’s twin-turbo DOHC V8 engine is being built at the Corvette’s engine plant in Bowling Green, Kentucky, and is an all-aluminium unit rated to 410kW and 850Nm

However, GM can’t use the Blackwingit in the C8, as it is exclusive to Cadillac. Cadillac President Steve Carlisle told Motor Trend that Corvette engineers would only get access to the engine “over my dead body”.

The Blackwing is a hot-vee design, with the turbos nestled between the cylinder banks, while leaked CAD drawings of the C8 engine show a more traditional set-up with the snails hanging off either side of the engine. Also, the Cadillac unit will have a traditional crossplane crank.

But, that’s not to say that the Cadillac and Corvette engines won’t be heavily related. It’s likely the duo will share the core block, though the C8 will have a changed bore, as the Blackwing is an under-square design, with a longer stroke than the diameter of the cylinders.

While this is good for reliability and torque, it’s not preferred for higher-RPM applications, like say, a race car, which is the whole reason Corvette is going to a twin-turbo layout.

Solid confirmation of what engine will be fitted to the Z06 will happen when the C8.R is officially revealed later this year.

We’ll need to wait a little longer to know how much power the road car will produce though, as GTE regulations often see kilowatts reduced in the name of BoP.