 The extra power (up by 25 percent) was the result of dished pistons containing the compression chambers, allowing for a flat cylinder head, providing higher and more even compression.While commonly referred to as a Heron head, Volkswagen called the design "HCS", for High Compression and Squish.The carburettor remained a twin-barrel one, and the only transmission at the time of introduction was a very long-geared four-speed manual.