I also see the locked timing thing or spec motor thing come up. I'm not a fan of those. Timing is too dependent on driving style and not being able to clean a motor helps nobody. Due to personal experience in a spec 2wd buggy class, I also would recommend that tracks who do a single spec class should make the spec slightly hotter than the regular class it replaces. The reason why is that during the transition from regular stock to spec, there will be holdouts and guys who are on a budget. The regular stock will always be run together with the spec class if there are only 3 or 4 of each motor. When slow spec motor the same wind as hot team motor has crashers outrunning the spec drivers down the straight, the spec motors disappear fast. A slow spec 13.5 could run with hot 17.5's with less of this. At that point it wouldn't be worth swapping motors back to a hot 17.5.