People think I’m makin’ this stuff up about the Italian Tune-Up. Bill de Creeft provides a quote from a British car magazine after the HE engine came out: “...if one runs the car for not less than a working week of relatively gentle driving, typically commuting with no longer journeys between, then, once properly warm, accelerates flat out, the engine goes through a period between 4500 and 5000 rpm of loud detonation accompanied by pale but noticeable exhaust smoke. You learn, after the first rather frightening occasion, to keep your foot down regardless, to accelerate through the knocking which, together with the smoke, stops and doesn't return until after the next period of town running. Jaguar,and Michael May, say that in gentle driving or with a lot of cold starts and short journeys combustion deposits build up in the head and on the valves. On hard acceleration these deposits heat up and burn, causing detonation but clearing, as they burn off into smoke. Jaguar says that in tests they conducted before the engine's launch (in July'81) in which such deposit-induced detonation was sustained artificially for long periods of hard running, showed no sign of piston or head damage.”