I was talking about that, if piston goes below bottom line of exhaust port it will not hirt at all ( but should be certain number).
Exhaust timing will have nothing to do with that ( exhaust timing counting from top line of exhaust port).
Actualy underpiston induction ( when gap is open at piston in TDC position) is using widely in couple classes in airmodeling ( if they not prohibited). In cases where carb diameter is restricted-underpiston induction is very good solution. In our case it will not unfortunately work due the presents of idle.
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