Enlarging PRP doesn't always help

PRH said

Depending in what you’re working on, without a proper form on the SSR……you could still be leaving a bunch of flow on the table.

With many stock heads(and some aftermarket heads too), when fitted with oversized valves and the bowls enlarged accordingly………the overall SSR form actually gets worse.

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Ahh, the bowl. Mystery area number two. Conventional wisdom says big bowls slow the air down to help it get around the turn. It also creates a large reservoir of high pressure air that is waiting to get into the cylinder the second the valve cracks open. The theory says that its good for torque.

On the other hand, a large bowl on a head with flow separation issues is not a good thing. If the bowl is larger in area than the apex area, the head has diverging(expanding) flow across the turn. Expansion of the air is a contributor to separation. Converging and accelerating the air helps prevent separation. Decelerating air efficiently is difficult, especially if the air is already in the process of turning.

This is where the dyno or track is really needed. Not going to answer this question with the flow bench.