Pushrods, Be Gone: Corvette to Gain a DOHC V8 in 2018

Michael Accardi
by Michael Accardi

It appears the Chevrolet Corvette is in line to receive a new dual-overhead cam V8.

An internal GM document detailing 2018 model year VIN codes was posted to the GM Inside News forum, and down on page five is buried treasure: “Passenger Car Engines for GMNA.”

The very last entry is a unicorn — the long rumored LT5 small block. General Motors lists the engine as “GAS 8 CYL, 6.2L, SIDI, DOHC, VVT, ALUM, GM” under code “Y”, which denotes the Corvette family.

In the past, there have been internal studies using DOHC heads on GM’s venerable small block architecture, but nothing came of it until now. On the surface, it would seem the big gain from adding overhead cams will be better breathing, as a DOHC setup allows GM more freedom when it comes to variable valve timing on both the intake and exhaust sides. The pushrod LT1 is limited to a set valve timing, as the single camshaft hits intake and exhaust at the exact same degree.

Where this will get interesting is in terms of packaging. How will GM manage to fit the larger DOHC heads under the Corvette’s low slung hood? Then again, the LT4-equipped Corvette Z06 does have a supercharger and two intercooler bricks tacked on top of the heads, so it might not be as tight a fit as imagined.

In other 6.2-liter V8 news, the supercharged LT4 is listed for A,Y, and K code cars. “A” denotes the Alpha platform (Camaro, CTS, ATS), Y means Corvette and K is the Omega platform that currently only underpins the CT6. It’s too early to proclaim that the CT6 will get a supercharged V8, but it is believed that Omega will find its way under other high-end GM products.

[Image: General Motors]

Michael Accardi
Michael Accardi

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  • Dukeisduke Dukeisduke on Dec 28, 2016

    Everything old is new again. Only this time, the engines won't be assembled in Stillwater, Oklahoma, but likely in Wixom, Michigan. Here's a very good post-mortem of the original ZR-1, from the September, 1995 issue of Car and Driver: http://www.caranddriver.com/features/chevrolet-corvette-zr-1

  • Drewtam Drewtam on Dec 28, 2016

    No comment yet about the "SIDI" acronym (spark ignited direct injection)? Switching to direct injection is also a pretty big head rework, and can increase the height of the engine.

  • Fordson Fordson on Dec 28, 2016

    Coming to this late, but I'm really surprised that no one has pointed out yet that one reason GM is hitting a wall with the 2-valve OHV is that the cylinder deactivation system they use in these engines doesn't like to rev beyond 6500 rpm...that's the reason that the LS7 is going the way of the dodo...it made 505 hp, but it did it by revving to 7k rpm...since you are not going to make EPA highway mileage targets in an over-6-liter engine without cylinder shutdown, all other current and future SBC versions have to have it. And since you're not going to make mid-400 hp with a 2-valve, OHV N/A engine smaller than 6 or so liters in size...that's how big it has to be. Everyone is really happy that the current 6.2L versions make 460-465 hp, but not so happy that at the 6500 rpm at which that power level is reached, there is a rock-hard fuel cutoff. They could make over 500 hp with these new engines if they could rev to 7k, what with the VVT that they have now, but the way they had to incorporate cylinder deactivation, revving to 7k does not meet their longevity and durability targets. it's a heck of a lot easier to implement cylinder deactivation when you have separate cams for each bank, and easier yet when you have separate cams for intake and exhaust. So they limit them to 6500 and use forced induction to get to the power levels they need.

  • Detroit-Iron Detroit-Iron on Dec 29, 2016

    To paraphrase Dr. Ian Malcolm "your engineers were so preoccupied with whether or not they could that they didn't stop to think if they should. "

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