In essence tho, there isn't a huge difference between the nitro funny car engine and the larger aircraft engines, large capacity, superchargers etc, but more importantly limited rpm range. Funny car engines are actually rather limited with their rpm range, the clutch does all the work of loading the engine actually. Which is one reason why the exhaust systems are rather similar - open pipes. As far as burning valves, that happens because of the uncorrected leanness of mixture that will generally occur when you take the exhaust system off. A properly tuned engine won't burn valves just because it has no exhaust to speak of. But if it was designed and tuned for one, and you remove it, that's another story.