People need to keep one thing in mind. I'm not aware of any area of the country that runs AMA 424 stricly to the rulebook. Most have variations in one way or another, usually more strict, but not always. If running other engines would help racing in your areas, ALLOW THEM!

The current 424 rules were bases somewhat on the APRA rules. I'm not aware of exactly who or how the 424 engines are decided, so I'm going to state what I know about the APRA class used on the west coast. When the APRA class was started, the engine list was much larger, and included almost every "sport" 40 size engine under the price cap. People would go and buy whatever listed engine that their local hobby shop had. They'd then show up at a race and find that their engines were uncompetitive, and complained that they bought a listed engine, so they thought they'd be competitive. Some never came back. To prevent it from happening in the future, the engine list was substantially shortened and limited to engines that were competive. As some of them then went out of production, the list was left with the Thunder Tiger. Yes, there are engines that are similar in price an performance, for example the Magnums. A handful of Magnums were tested and found to be far more inconsistant from engine to engine, from considerably stronger than the best TT tested, to well below the worst. It was decided to stick with what had been fairly stable and had been working. Also keep in mind that APRA rules do have a provision to allow other similar engines (IE no Rossi's, ect) for a competitor's first race or two, with the CD's approval.

Personally, I'm not in favor of the entry level events being AMA rule book events for one primary reason. The AMA rules cycle is too limiting as far as making changes. Rule changes can take well over a year to get done. As an example, if the Club 40 events, which are very successful in some areas, were in the rule book, what would happen if the manufactures of those airplanes were to quit making them for one reason or another? Legally, other airplanes couldn't be used per the rules, therefore effectively killing the event. If the class was left as a grass-roots event with flexible rules, other airplanes could easily be made legal.