If you consider how AMA did it back in the day, it doesnt seem so strange. We had a C engine class, which drew its basis from both flattrack and AMA roadracing. There were certain basic requirements, such as cases, head casting, etc that allowed an engine to meet the C rule. If it didnt, it could run AG or AF engine (mod gas or mod fuel). Those various C engine rules translated into the different frame classes for Bonneville, but C engines came from an older mod allowance system for production based engines.
It was possible to run two different engine classes (C and AG) in the same chassis, at the same event (I did), but you understood you could be giving up something running your C against an AG engine. In my case it was displacement, because I only had the legal amount of C overbore permitted in my 450 Honda. As an AG engine, I could have been 500cc, but I only had the 468cc allowed in a C build.
One of my competitors was a Norton Manx 500 single, who had to run AG engine class with a "stock" engine because the Manx had insufficient production numbers to qualify for C engine class! Here, the general low availability of the engine influenced its lack of C (production) status.
I'll bet I'm not making it sound right.... Still and all, there is logic to their method....its just different from SCTA. Interesting stuff, I think, and very difficult for the inspectors.
Regards, JimL
