The V8s are a tough call for GM, IMO. Caddy absolutely must sell a DOHC lineup - 4 / 6 / 8. Both the 4 & 6 perform well but have been criticized for being noisy compared to Europe's best of those engines.
But the SBC in all of its OHV versions has always proven to be extremely versatile for tuning [power / torque / economy], packaging and weight - especially torque in the trucks. However, as CAFE increases rise dramatically (even though the 53 MPG will be pushed out later years) intake / exhaust controls require more fine tuning than two valves can provide.
The most efficient answer is one that is risky given today's technology level: cam-less. For years they have been working on opening and closing valves using individual, computer controlled solenoids to determine lift and duration.
Basics (please forgive the elementary information and feel free to skip this):
The head forms the round top of the round combustion chamber with round valve(s) to enable intake of fuel/air mixture and round valve(s) exhaust spent gases. The more valves there are in the chamber, theoretically, the faster the mixture can get into and the faster the exhaust can leave, the chamber. These days they even know where in the chamber and what shape the mixture is forming in the chamber.
Advantages of solenoid valve control:
Please note that I am NOT an engineer so for those of you who are, please chime in if I have misinterpreted or omitted important issues about computer controlled electronic solenoid valve controls
1. No cam, means few moving parts; less drag and less metal wear being circulated throughout the engine.
2. All specs being equal, the solenoids would likely be lighter than cam(s). Realize that the challenge is not only the reliability, but also the compactness of these solenoids.
3. Physical valve arrangement would no longer be determined by the placement of a cam and mechanical valve train. Need more control over the mixture in the chamber? ... how about 6 or 8 small valves? Probably inefficient, but you get the point.
4. This is implied above - better capability to control what is going on inside the combustion chamber. Think of this as Infinite Individual Variable Valve Timing.
5. Exhaust sensor results sent to the ECM enable immediate, minute, fine tuning of the lift and duration to assure minimum emissions / maximum economy / maximum performance from the fuel.
6. A 4 valve per cylinder solenoid engine would be significantly narrower and lighter than today's DOHC arrangement. No need for cam cradles and bearings.
Disadvantages of solenoid valve control
1. Today's valve train - springs, rockers, rods, cams - are very reliable and under normal conditions and maintenance, wear slowly and usually(but not always) alert the driver of problems before a cascade failure that destroys the engine. Failure of one solenoid leaving the valve in the down position would likely destroy the engine.
2. Availability, reliability, and the capacity of electric power for the solenoids is obviously critical. In the event of a failure in the electric power system (Battery? Alternator!!?), there must be enough reserve power to enable the engine to shut down normally (valves completing their close cycles).
3. Again - Not an engineer. I can't think of another disadvantage.
Will we see this high tech on the C8?
IMO, it would be shocking to see solenoid valve controls first appear on a V8. If I controlled one of the BIG car companies when the tech was ready, I'd apply it to a 3 cyl Hybrid first. Less to replace if there are problems and most likely to be able to "limp" into a dealer when the lights and buzzers go off because of a failure. Also a deeper reserve of electrical power is available.
IMO, either this technology will come to production soon, or the gasoline engine will be legislated into extinction....in fact, this might happen anyways, eventually. Faster if Clinton is elected. Just a fact, not a political statement.