I remember going out as an RAC patrolman to an HC one evening in the late 70's on the A1, burning oil, running like a pig on three cylinders. Two elderly ladies in the car heading home somewhere up north, RAC rescue, not recovery membership. Engine had a holed piston, I pulled the rocker cover, rockers and pushrods on the duff cylinder, topped the oil up and away they went, on three cylinders, no smoke, running as sweet as a nut, try that on a modern engine!
I seem to remember they also used to burn through the "hot spot" between the manifolds, resulting in an early example of E.G.R.