This design had an exposed valvetrain (you could see the pushrods and lifters from the top) with nickel-plated rocker cover, an aluminum water-cooled intake manifold; the starter is in the valley, as is the gear driven generator with the fan clutch coming off of it.
The engine was a development of the old 2.5-litre Standard pushrod unit converted from side valve to overhead valve with a new cylinder head designed by William Heynes and Harry Weslake.
In an effort to appeal to smaller engine-building companies, USAC had permitted "stock-block" pushrod engines (generally defined as single non-OHC units fitted with two valves per cylinder actuated by pushrod and rocker arm).