Sam Heron – pioneer

Regarding Sam Heron (1891 – 1965) and motorcycles ( OBA 57 Letters), subsequent history indicates that Sam Heron, in retrospect, was probably the most prophetic theorist of the modern reciprocating internal combustion engine. Working for Standard Oil on the development of high octane fuels using aircrafttype 4-valve single cylinder slave engines since about 1930 he came to several conclusions, amongst which were to have the shortest and most direct gas flow possible, and to change the then-current perception of the combustion chamber believing it should be seen in a dynamic sense and not as a space in the head. Among the first users of his principles was Rolls Royce in their Merlin engine as early as 1939 after trying other alternatives. The Merlin featured four vertical valves in a relatively flat head and concave pistons – often simplistically referred to as having the combustion chamber in the pistons. Examination of drawings of the later WW2 German Daimler-Benz DB 603 aircraft engine shows a similar configuration.

In the early ‘60s Rover developed a 2-litre 2-valve OHC car engine using some modified practices which was promoted for publicity purposes as having a ‘Heron head’. A little later the 2-valve Moto Morini was also described similarly. Drawings of the DVA engines show clearly that it follows Heron’s principles, in fact Mike Duckworth, later commenting on his design, said that he came to the same conclusions as Heron, independently. To call it a ‘pent roof’ design implies it was a semihemispherical head layout with opposing valves. This was not so. It clearly used a so-called piston-top