When I write this, it is just about seventy years ago I heard high speed spark and diesel engines spring to life for the first time after being overhauled in our familyowned shop, and I got hooked forever ... To hear the bark in the exhaust and see shafts and flywheels whirling, it was fascinating for a four-year-old boy ... Done by my dad, my uncles and the employees in the shop. This startup was done outside under the tin roof ... on a concrete floor. Inside, several engines, all in pieces ...: There were stacks of parts and pieces - new and old - that were readied and next assembled, .timed", adjusted etc., to become a live unit that could power a boat, a car, a truck, a compressor, an alternator/generator, a pump, a tractor, a crane, a bulldozer, a motorcycle. I wasn't that old when I could identify many different diesel engines in trucks and buses by sound ... I did not see them, only hear them: It's a Volvo, Leyland, Perkins; it's a Mercedes, it's a Deutz, it's a Scania. They all had their own distinct ignition knack to my ears ...the crackle. And ... powerful spark engines in fast boats that were tested out in the Byfjord and I was allowed on board if I promised to sit still in a corner. It was thrilling for a little boy: They hand-tuned the ignition advance; they also hand-tuned the mixture strength on many American made 6 cyl. marine engines that had updraft marine carburetters ... fast engines made by Gray-Marine and Chrysler. The test instruments were the mechanics' ears and brains ...: Tune safe ... a bit away from spark knock, and a tad rich on the fuel mixture ratio to not burn valves and spark plugs. I looked with big eyes when the grown-ups did their magic". And ... my dad was the biggest magician ... He had this special sense when it came to engines, using the tools involved, and tuning for max performance ... be it spark engines or diesels.