The Over Head Valve (OHV) pushrod engine is old. Really old.
Rudolf Diesel designed the rudimentary OHV design in 1893, with Henry Ford’s 1896 Quadricycle using the design. Then came David Buick who designed the modern OHV V-8 engine in 1902 for what would eventually become the Buick Motor Company.
It has been over 125 years since this design was first introduced, yet we still are designing brand new engines (Ford’s 7.3L Godzilla) with this design.