Surely the Hercules was later than ’36.
The 1,550 / 1,000hp Taurus (developed via the 9 cyl single row Aquila – first sleeve valve engine) was the first usable double row sleeve valve from Bristol, it first ran in ’36.
The Hercules was Perseus based and development ran just behind the Taurus.

Impact wise, if the engines were available earlier, I guess greater things could have happened, especialy with bomber and transport design.