Racing motorcycles and Bonneville cars run bent valve stems with the cap end set in the trailing position, to lessen the possibility of centrifugal force sucking the valve core down & losing air at the worst possible time even with a cap. The usual ones are 80 degree aluminum valves. They will not fit a stock Campy drilling but for your aftermarket wheels, they may fit or simply drill a new hole. I got mine decades ago; Google 'angled valve stems'.
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