Wayne
You must have Subaru on the brain. They only come in 1600cc>>2000cc>>2500cc's. They were just a little too big.
Were I to write the engine rule, I would say something like this. Engine must be readily available in USA in large enough quantity to be easily available to all racers, (proof of 2500+ in production). Limited it to 3000cc's. Any 4 cycle engine of any cylinder configuration would be allowed. If engine came stock from factory with forced induction the displacement would be limited to 2000cc's and Boost would have to remain set at stock factory specifications, to be monitored by sanctioning body with a Data Acquisition device, (could be something very simple and inexpensive). Bore and stroke would have to remain at stock specifications as the engine being used (NO ALLOWANCE FOR CLEAN UP). Stock sized HD valves and HD Valve Springs would be allowed. The use of any aftermarket engine blocks, heads, crankshafts, camshafts, rods, and pistons would be forbidden. NO PORT ALTERATIONS would be allowed. Oiling, carburetion, Ignition, and engine management would be optional. No traction control.
Don't limit brand of car or model (or for that sake don't even limit it to automobile, it could be boat or snowmobile) motor, who cares. The Porsche, Ferrari, etc and other hot cars and motors would lose out because of production #'s. BUT it would sure open up the field to lots and lots of engine configurations and yes there would still be the engine of choice and probably not one of the engines set forth in the rules as they are written now. And speeds would increase
Honest Dad himself
