DAP T73: the first water-cooled 100cc engine

Columns: Legendary kart
DAP was the first manufacturer to design, develop, and race with a 100cc liquid-cooled engine from 1978 to 1984. It won practically everything before someone decided to ban it from competitions… (p.m.)

For the 1978 homologation, Angelo and Achille Parilla’s DAP surprised the karting world by launching the first water-cooled engine: the T73. Even in those years, DAP was at the top with a driver like Terry Fullerton, and the T70 and T75 engines were in high demand thanks to their numerous victories worldwide. However, the Parilla brothers had one of those moves up their sleeves that made them famous: the DAP T73, the first water-cooled engine for the top category of direct drive karts.

To be precise, DAP’s liquid-cooled engines were two: the short-stroke T83 (with bore and stroke measurements of 50.8 x 48.5 mm) and the long-stroke T73 (48 mm x 54 mm). Given the limited time available for this new project, Achille chose to develop the T73. The starting point was the T72, an engine that lagged by a couple of tenths of a second behind the more performant T75, but the choice was made to avoid this prototype potentially disrupting the sales of the air-cooled T70 and T75 engines, which were then absolute best sellers.

Despite this handicap, due to a less efficient crankcase in terms of transfer ports, the T73 immediately proved devastating: a real scare for the competition. The new liquid-cooled cylinder was mounted on the T72 crankcase, its external shape clearly inspired, on a larger scale, by one of the cylinders of the multi-world champion 125cc MBA, thus ensuring optimal coolant circulation already studied. The cylinder design was by Giordan Giordano, a skilled technical designer at DAP. The liner maintained the 3-port configuration with a split exhaust port with a bridge. The engine was developed at the beginning of 1978 and was tested at the 1979 World Championship in Estoril, even on the legendary short-wheelbase DAP WTR chassis, the green one with number 17, which the Brazilian champion liked so much. However, suspicious and deceived by the absence of vibrations typical of water-cooled engines, he demanded a standard T70, the same as his teammate and rival Terry Fullerton. What a pity: with the T73, he would have won the world championship...

Achille Parilla kept a couple of engines in the racing department, one mounted on a ready-to-use chassis, and every time he put it on the track, it won crushing victories accompanied by controversies from the opponents. In 1983, Stefano Modena, followed by Giordan Giordano's brother Renato, won all the races he participated in with the T73, about 23, leaving opponents with embarrassing gaps. For instance, in Parma, the DAP T75s used a 10/78-10/77 gear ratio against the 10/82 of the competition; the T73 managed to pull a 10/72, which says a lot about how much more powerful and faster it was than the competition.

In the 1983 Italian Championship, there was a resounding victory by the T73 by the eighteen-year-old Umberto Borghetti, but the driver was disqualified for half a degree of rotary valve timing: the winner under the checkered flag was in fact 1.2 seconds faster than the other competitors! A flight to Rome by Borghetti (who lived in Milan) accompanied by Achille Parilla was in vain: the ridiculous disqualification was not annulled.

The T73 made a comeback in 1984 with a crushing victory by Vincenzo Sospiri, who won the 100 Avenir Italian Championship with this legendary engine before the federation decided to exclude it from competitions for its manifest superiority. Angelo and Achille Parilla accepted the federation’s verdict, agreeing with the desire not to trigger an excessive increase in costs (different times, different men). The DAP T73 was produced in fewer than 200 units, and a reed valve version was never made.

Today, these engines are very rare, as is the dedicated magnesium cast radiator support, and it is perhaps the most sought-after 100cc engine by enthusiasts and collectors.

Created by: fmarangon2 - 20/05/24

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