GM Debuts New Architecture, DOHC 4.2L 550hp Twin-Turbo V8

When the big daddy Caddy CT6 debuted last year with a twin-turbo V6, the automotive world gave the equivalent of an eye roll.

With a former German car executive running Cadillac, it was probably just a matter of time before we saw a true Autobahn contender from Cadillac, even though the Wreath and Crest division only sells cars in the U.S., Canada and the Middle East. With it’s smaller stablemate CTS-V packing big-cube V8 horsepower for years, we wondered what GM had up its sleeve for a future big kahuna version of their top-of-the-line entry.


Behold, GM's brand new, Cadillac exclusive, DOHC, 4.2L 550hp, Twin Turbo V8 engine.

The introduction of this motor has many repercussions. Not only about Cadillac and it’s ability to regain “Standard Of The World” status, but also gives a crystal clear glimpse into GM’s commitment to the internal combustion engine and the future of gasoline performance from the biggest U.S. automaker.

According to Cadillac, their new V8 is a “DOHC, 4.2L twin-turbo V-8, a clean-sheet design three years in the making and exclusive to Cadillac, makes an estimated 550 hp and 627 lb-ft (850 Nm) of torque. A detuned version with an estimated 500 hp and 553 lb-ft (750 Nm) of torque also will be offered. The engines are mated to a Hydra-Matic 10L90 10-speed electronically controlled automatic transmission and all-wheel-drive only. Fuel economy and emissions ratings will come later.

Wards Auto elaborates further, “The Cadillac V-8 uses a “Hot V” design, where the twin-scroll turbocharger and electric waste gate are mounted in the valley between the aluminum cylinder heads to minimize turbo lag and overall engine packaging. The catalytic converters also are nestled inside the V.

An aluminum cylinder block houses a rotating assembly consisting of a forged steel crankshaft, forged steel connecting rods and high-strength aluminum eutectic pistons. Relatively small, 86-mm cylinder bores allowed engineers to reduce the size and weight of the pistons, which optimizes the engine’s geometry to match fast-revving turbo boost and deliver lightning-quick responsiveness and power across the rpm band.

Torque delivery focuses on the low- and mid-range rpm band, GM says, with 90 percent of peak pull available at 2,000 revolutions. It continues through 5,200 rpm for the feel of a bottomless power reserve, the automaker says.

Key technologies include gasoline direct injection and active fuel management, where four of the engine’s cylinders are deactivated under light loads to improve fuel economy. GM has a next-generation cylinder-deactivation system coming out with the capability to run between one and eight cylinders depending upon load, but the timing of the Cadillac engine was too far ahead to get the latest version.

GM places four oil jet assemblies within the block to aid in cooling and uses a variable-displacement vane oiling system to match oil supply with engine load for greater efficiency. Stop/start technology also improves fuel economy.”

The engines will be hand-built at GM’s Bowling Green, KY, Performance Build Center, a part of the Chevrolet Corvette assembly plant where the Corvette Z06 LT4 small-block V8 are screwed together. Each of the new Cadillac engines will be autographed with the builders signature.

The rather blandly named “Twin Turbo V8” will debut in the 2019 Cadillac CT6 V-Sport–not V Series–at the New York Auto Show on March 28th, 2018. This is the first Cadillac exclusive V8 since the Northstar and will go a long way to injecting some sales momentum into the excellent, but a tad boring, CT6. The new CT6 will also have Escala-esque styling updates adding some exterior pizazz to go along with the new motor.

Car folks have cause for celebration here, but many questions arise from this introduction.

What other Cadillac could get this engine?

The Escalade is a logical recipient. Differentiating itself from the Denali with an exotic V8 could further delineate the ‘Slade from it’s sister model and justify an even higher- end model. It’s rumored that only 1,500 of the new V8s are slated for production, so that scenario is a giant “Wait and see,” although adding the motor to more models could pay off its development costs faster.

Top: Not Caddy’s first time at the DOHC rodeo…Bottom: Escalade ripe for new V8

What about the ATS and CTS? The new V8 is smaller and weighs less than the LS/LT motors and would fit in both but that’s unclear at this point as well. On the other hand, spreading the motor all around nixes the exclusivity of an individually assembled engine, too.

Will We See This Engine In C7 Corvette Or New Mid-Engined C8?

Building the new engine at Bowling Green is telling as well. We’ve heard about a mysterious DOHC Twin Turbo mill for months as we anxiously follow the new C8 Corvette development. We think it will debut in a Corvette at some point. We also think this engine will see a displacement boost and big power bump when it lands in the new Corvette as GM always introduces the “mild” version first.

Will Camaro See This Motor?

For years, the pony was never to outrun the horse, i.e. the Camaro couldn’t trump the Corvette. That was all thrown out the window a few years ago and now the Camaro gets everything it’s big brother gets. A Camaro with a hopped up version of this motor would be the final nail in the coffin for Chevy pony car critics. Can you imagine their faces? How about the import crowd? What malarkey excuses would they come up with if the pushrod motor complaint was banished…forever?

What Does This Mean For the Future Of The LS/LT V8 Family?

GM needs truck motors so the notion that this will replace our beloved pushrod LS/LT small-block V8 anytime soon is far-fetched at best. We might see this as the sole architecture for V8s if GM migrates it’s trucks away from eight cylinder power. Ford tried this with mixed results so we’ll have to see.

Current LT1 not in danger…Yet.

Is This The Hot Rod Crate Motor Of The Future?

We think this thing would add alot of spice to the hot rod scene. From ’69 Camaros to ’32 Fords this thing all dolled up would be a real killer. Or is it too fussy for the old car gang? Maybe, but guys have been transplanting Lexus DOHC V8s and Northstars for years, so let’s not assume anything. Is there a new crate motor from GM Performance in the future as well? Lighter and smaller than the LS/LT family, it might an easier fit between an old car’s frame rails as well.

Pete Aardema’s roadster that showed up at GNRS 2018 runs a Cadillac Northstar. These engines were transverse mounted, front-wheel drive in stock form. Cadillac Hot Rod Fabricators makes components to convert them to conventional rear-wheel drive. What else do you need? Cams, pistons, rods, intakes, turbos, cam covers—they make all flavors of Northstar to make it a high-rev, 480hp, fuel-injected performance engine. Or blown. Or turbo—whatever you want.

ICE Engine Alive And Well At GM?

With the Volt, Bolt and spending millions on Maven and Cruise, GM big cheese Mary Barra has been touting an “Accident-free, emission-free, traffic-free future” for a while now, so this news is a big sigh of relief for petrol heads. It shows that GM is continuing to develop internal combustion engine and will do so for the foreseeable future.

Commensurately, is this the last clean sheet gasoline motor from GM? Let us know your thoughts in the comments below.

The CT6 V-Sport arrives at U.S. Cadillac dealers in the first half of next year, with rollouts in Canada and the Middle East closely following. Pricing will be released closer to launch.

About the author

Dave Cruikshank

Dave Cruikshank is a lifelong car enthusiast and an Editor at Power Automedia. A zealous car geek since birth, he digs lead sleds, curvy fiberglass, kustoms and street rods. He currently owns a '95 Corvette, '76 Cadillac Seville, '99 LS1 Trans Am and big old Ford Van.
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