Oh boy, not this again.
You guys have to realize there are variables to OHV that is not incorporated by Automation, two of them being the leading contributors to how they make power.
Solid Lifters vs Hydraulic Lifters (our simulation uses Hydraulic)
Roller valve train vs journal type (our simulation used Journal)
On hydraulic lifter engines the valve lifter is a hollow tube with a spring inside connecting the pushrod to the camshaft. The lifter is filled with oil pressure from the engine to act as a cushion, and the engines are run at zero lash (very quiet) because of the nature of this valve train and its low tolerance for high resistance, soft valve springs are used and this engine combination exibits early valve float.
On solid lifter engines, the valve lifter is as its name states, solid, the connection between the pushrod and cam is instant via the lifter which were manufactured with a high zinc purity. These engines run valve lash (a gap between pushrod and rocker) so the initial ramp of the cam lobe can be climbed by the lifter. Since the base between the cam and push rod is solid, heavier springs can be used in combination with longer duration and higher lifts. In the 50s-70s this was how OHVs made any power, and these engines had an upkeep which was triple the normal hydraulic engine.
Journal style valve train: This is the model our game uses, and this is the model all OHVs used up to the late 80s. The rocker arms are simply riding on a shaft which is injected with oil, the lifters are all flat tapped bottoms which ride directly on the cam lobe, the pushrods are in direct contact with the rocker arms in a polished socket and are normally oiled to prevent ware, and finally the rocker arms directly press on the valve stem. Everything is metal to metal and there are frictional loses.
Roller valve train: the lifters all ride on bearings against the camshaft, the pushrods all press against end caps on the rocker arms which are encased in a bearing, the rockers themselves ride on a bearing, and the rocker tips which press upon the valve stem are on a bearing. This setup has the lowest friction loss, and is expensive. Hybrid roller setups have been used since the 80s, and full roller setups since the late 2000s (The LS was not a full roller engine, not initially)
So, with our simulation you will never see the wild claim of power made by the US manufacteres in the 60s, this is for two reasons:
A: We are simulating the every day OHV, Hydraulic/Journal.
B: The US manufactures cheated on Dyno day. SAE Gross was measured with no equipment on the engine, in an ideal situation with ideal fuel and timing. At minimum expect SAE Gross figures to be at minimum 25% high.
As Killrob mentioned, OHC tech was banned from racing in the US, in 1964 Ford released a converted 427 FE engine which was OHC, it was banned by the NHRA, and NASCAR because it provided an un-competitive advantage
At this point in development it would ad un-needed complexity, but if for some reason we wanted to add it in, the OHV engine would need two additional options.
1: The option for Solid or Hydraulic lifters. Solid taking a reliability/smoothness/maintenance hit, with only a gain in valve float.
2: Full roller, Roller Lifter, or Full journal: Full roller would have the highest engineering and PU cost, offering a slight gain to efficiency, Roller lifter would be a smaller commitment to engineering and PU, and what we have now, Full journal.
Why did I have to read this, sorry @Killrob