We don't allow any variable duration lifter (too noisy for a hydraulic cammed car) since it is a red flag/dead giveaway for softening/hiding a bigger camshaft, but mainly, we want the cars to look and sound stock, on top of having all the correct casting numbers. We know racers are racers, and very competitive looking for any advantage they can find, and, if they figured out how to make a quiet variable duration lifter, good for them, they won't be scrutinized. I wouldn't be surprised if there are a few creative and inventive guys/gals who machined a lifter innards to bleed down a little faster without making noise, more power to them, as long as they are quiet, we won't know the difference. As long as thy can make the 18" vacuum at 1200 rpm, and do it quietly with a hydraulic cam, they are legal.
Dennis
|