[Jim Brierley]

From Alexiskai, Maybe better phrased as "compression and airflow" – after all, when you switched to the downdraft carbs I'm guessing you installed a new intake manifold.

Compression alone will improve performance at low RPM, but airflow is key to unlocking performance at high RPM.

Yes, I did switch manifolds as well.

On reground cams. A stock regrind will perform as well as an original stock cam. The difference comes when you go to a 'touring' cam or 'race cam'. Modified cams move the power/torque range up the RPM scale, and take advantage of the inertia of the air entering the cyl. Performance cams need, carb and compression, bigger intakes, ports, etc. to reach max HP. A lot of engine builders install bigger intake valves, not much if any advantage in an otherwise stock engine. The small stock carb limits the power, not, IMO, the valve size. A high-performance cam installed in an otherwise stock engine will actually hurt performance. High valve over-lap won't allow good air flow at low speeds and the small carb won't allow much air flow at higher RPM's.