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Efficiency and valve trains can be less connected than you might think.
Delage racing engines in the 1920s and early 1930s had 60 ball and roller bearings and the engine block and heads were cast in the same unit to eliminate head gasket failures.
The stock block Indy engines were allowed significant displacement advantages over the turbocharged specialty engines.
One example I remember was the Alfa 8c engine developed in the 1930s. In the early post WW2 era in grand prix racing trim they produced 390 HP out of 90 cubic inches at 2 miles per gallon.
Since best mileage is achieved at lower speeds and many times with higher rates of EGR, it may be we actually go back to smaller valves, and less effective cylinder scavenging, with higher turbulence at lower RPM.
It would be interesting to take some of the older designs of many decades ago and use modern fuel delivery and ignition technology to see what could be done.
My old 37 Ford with the original Flathead V8 would idle at 350 RPM and glide down the road in high gear at 7 MPH idling. Max revs were 3800 RPM.
The engine weighed 525 pounds. The whole car was lighter than a Toyota Corolla.
regards
Mech
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