1971 Duster 360/727

It's the tip of the rocker. The roller rocker rolls her the top of the valve stem freeing up HP. There actual ratios are very consistent. Normal ratio is 1.5. A 1.6 is available.

Ordinary rocker, as in the OE (Original Equipment) are stamped steel parts that rub on the valve stem costing HP. Also the OE rockers are very bad in there actual ratio. Sometimes coming in as low as 1.3 instead of 1.5.

I am not totally on board with a larger 2.02 valve losing torque on the low rpm.
The smaller valve will keep velocity up. But give up HP up top. There are also a lot of other factors that will give up torque on an engine than a 2.02 and be more than a good bit more serious in loss. Poor tune, too large of a carb, wrong cam, low compression.

Any engine I'm building now gets a 2.02. My cast crank engines run mid & low 12's for the last many years. There's more than a few guys here producing well over 450 hp on cast cranks.