So you have your flame suit ready...lol....


like you said here is the rule from the site..........

3. Engines

a. Any side exhaust two cycle engine up to .61 cubic inches is legal
b. Four cycle engines up to .91 cubic inches with no air chamber or super charging or any kind are legal
c. A proper muffler must be used but tuned pipes are not legal d. Pumps may be used but no oversized carburetors can be used.

so if it said muffler on the package , I would think it would be legal.. I think there where a few used at the SPA Masters in 2010....

It is legal in CPA www.classicpatternassociation.com