exhibit B
Wiki GM
In 2005, the Generation III was superseded by the Generation IV. This category of engines has provisions for high-displacement ranges up to 7,011 cc (7.011 L; 427.8 cu in) and power output to 638 bhp (476 kW). Based on the Generation III design, Generation IV was designed with displacement on demand in mind, a technology that allows every other cylinder in the firing order to be deactivated. It can also accommodate variable valve timing.
A 3-valve per cylinder design was originally slated for the LS7, which would have been a first for a GM pushrod engine; but the idea was shelved owing to design complexities and when the same two-valve configuration as the other Generation III and IV engines proved to be sufficient to meet the goals for the LS7.
exhibit C
W43 oldmobile 32 valve two pushrod v8 early 70’s
exhibit D
Wiki - Ford
The Truck Division instigated a pushrod operated four valve per cylinder, cylinder head conversion in the early 1990s as a means of modernizing/improving and furthering the service life of the Windsor engine. This work was done for Ford by Roush Industries (for 1 million dollars) and two 302ci/5.0L and one 351ci/5.8L variants were built and tested. These engines were highly successful but upper management refused to allow engines so equipped to go into production stating that it was no longer acceptable to use a cast iron block in a new car – one of the 5.0L engines is out there in a hot rod.
and then there is this which can be taken with a grain of salt
and the patent for 3 valve OHV heads
https://www.google.com.au/patents/US6505589