I found some old fuel economy figures from when I was running a 4k.
Car: ke15 with a 4k (270 deg cam, portwork, 9.85:1 CR) + 5 speed running a 28/36 dcd Weber.
At the time I was doing some delivery driving in around the suburbs south of Brisbane. I did 1302 km for 101 liters of fuel. 7.76 l/100km or 12.89 km/l. On the cruise it was better. Not bad for a thing that would easily outrun your average 6 cyl falcadore.